Is there such a thing as “American fashion”? I don’t mean “American designers”, they clearly exist; or fashion made in America – that issue can be left to the politicians in Congress. No, I am talking about the more complicated question of contemporary aesthetic identity. Once upon a time, according to veteran US designer Michael Kors, “Paris stood for fantasy, Milan for luxury tailoring, London for quirkiness and New York for pragmatism”.

But, as the 2013 spring/summer womenswear shows kick off in New York, it seems an appropriate time to ask if there is such a thing as a national aesthetic any more? Can such a thing exist in a high fashion world where brands sell to clients who might live in Moscow or Beijing, shop in Paris and work in New York; where a company such as Paco Rabanne can have its headquarters in France, be owned by a Spanish company, and have, as it did at one point, an Indian designer; where ultra-Parisian label Yves Saint Laurent has chosen as its new creative director Hedi Slimane, who is planning to do his job many time zones away in Los Angeles; and where Brits Victoria Beckham and Stella McCartney can hold their ready-to-wear shows in New York and Paris respectively.

The obvious answer would seem to be no. But the real answer, surprisingly, is yes – at least as far as America is concerned. What’s more, American fashion is getting clearer, not fuzzier. Robert Burke, founder of an eponymous brand consultancy and former fashion director of Bergdorf Goodman, says: “There hasn’t been a moment like this in New York fashion since the Ralph/Calvin/Donna years [of the mid- to late-1980s].”

This is not necessarily symptomatic of wider fashion world trends: British fashion is not becoming more identifiably British than before, for instance. But a combination of factors – such as the blurring of old dress code rules, the rise of high street fashion, and the recession – has helped to create a new group of New York-based designers with a shared aesthetic. At its heart are clothes combining the simplicity of separates with luxurious and texturally rich materials and construction.

Think, for example, of Reed Krakoff’s green silk sleeveless dress piped in racing stripes of black leather with a subtle drape at the waist created without the aide of a belt ($1,590, worn by Charlize Theron among others); or Michael Kors’ lace and stretch wool-crêpe dress ($2,395), the lace offering a peekaboo effect in an otherwise simple silhouette. Think of Mary-Kate and Ashley Olsen’s label, The Row, and their military-style ribbed wool jacket with three rows of steel buttons instead of the usual two ($1,790). Think of Narciso Rodriguez’s white silk crêpe dress with black inserts for silhouette shaping ($1,695). All these clothes share an externally pared-down but internally pumped-up sensibility.

What to call this new movement? “I think luxury sportswear is the right term,” says Simon Collins, dean of the school of fashion at Parsons the New School for Design in New York (and, as it happens, a Brit). This term was once considered an oxymoron – luxury being by definition exceptional, rare and fragile, and sportswear being by definition easy, functional, utilitarian and basic – but in the modern world it makes high/low fashion sense. (Sportswear, of course, does not mean clothing for sport, but rather a form of dressing invented in America in the 1930s that, according to an essay by Richard Martin, former curator of the Metropolitan Museum’s Costume Institute, involved rethinking “fashion from its very roots, not simply paring away some of the accretions of traditional prettiness but establishing a new standard for a practical, modern style in accord with the lives of the women”.)

“Sportswear was always about separates,” says Collins. “And that is how everyone dresses now. The power suit has gone out of the window.”

In the early 1990s, when I briefly worked at American Vogue, even Anna Wintour wore skirt suits to the office; for the past 10 years, I can’t remember seeing her sitting in the front row of a fashion show in anything other than a full skirt and cardigan, or sheath dress. Michelle Obama, too, has eschewed suits in favour of printed dresses and cardigans. “We call them ‘editor-in-chief’ dresses,” laughs Kors. “When the word ‘sportswear’ came up in the fashion context, you used to get all this snide, ‘Isn’t that jeans and T-shirts?’ But not any more. People understand it means ease, and even an evening gown can have that.”

The shift has been acknowledged at industry level. At this summer’s Oscars of the US fashion industry, the Council of Fashion Designers of America (CFDA) awards, The Row beat Marc Jacobs and Proenza Schouler to take home the award for womenswear designer of the year; Reed Krakoff won accessory designer of the year, ahead of It bag darlings Alexander Wang and Proenza Schouler. The awards are voted for by the fashion community at large, so it’s effectively a jury of peers.

Coming on the heels of Michael Kors’ $944m initial public offering last December, the biggest IPO in American fashion, these awards seemed to announce the beginning of a new stage in American fashion. As Steven Kolb, president of the CFDA, said: “I think it’s an acknowledgement that what has always been the defining element of American fashion has evolved.” Put another way: there is a reason shares in a company run by Kors, effectively the father of luxury sportswear and someone who can make a camel pencil skirt look ineffably expensive, have more than doubled in price since the IPO; and a reason why Bloomberg recently ranked it the number one public offering of 2011.

There is, of course, more going on in New York fashion than luxury sportswear. Designers such as Proenza Schouler, Marc Jacobs, Oscar de la Renta and Kate and Laura Mulleavy of Rodarte all have highly relevant, lauded individual visions that resonate globally; the CFDA also acknowledged the rise of mid-range American contemporary market brands such as Rag & Bone, Theory, Helmut Lang, J Crew and Tory Burch and gave Andrew Rosen, godfather of the contemporary market, its Founders’ award. But what sets apart the sportswear movement is its visible embrace of an American fashion continuum, and its cohesion.

The period Robert Burke calls the “Ralph/Calvin/Donna years” was, indeed, the last time US fashion presented a coherent face to the world. This wasn’t because Lauren, Klein and Karan shared the same aesthetic – they didn’t and still don’t – but because their work was joined by a certain shared value system, built on words such as “easy”, “simple” and “functional”. It made for a hattrick of American fashion power that hasn’t been equalled since. All are, of course, still in business and bigger than ever – but they have become the establishment; the expected.

This aesthetic – call it power sportswear – was also rooted in the times: Karan and Klein, in particular, made power clothes for women who wanted to work their way to the top. It was stage two of the revolution launched in the 1940s by Claire McCardell and Bonnie Cashin, when they helped shirtwaists and other intrawar pieces transcend their origins with an injection of easy elegance, offering a local alternative for the first time to the European vision of fashion – one that was not rooted, as Simon Collins points out, in “dressing for court” but in functionality and relative informality. This was later adopted and adapted in the 1970s and early 1980s by Liz Claiborne and Anne Klein, who brought “American fashion” to the girl on the street.

Yet the roots of what Reed Krakoff describes as sportswear’s “third generation” took hold only recently. “I date it back about five years,” says Burke. “When American designers stopped trying to be Italian or French.”

The recession-hit 1990s, with its adoption of grunge, deconstructionism and Pradian minimalism, seemed to confuse American fashion, with its focus on functionality. It was, says Collins, a time when New York was very Europe-facing.

Though many terrific designers – including Marc Jacobs and Tommy Hilfiger – became famous in that period, their work was marked by an individuality that often made New York fashion week as a whole seem oddly diffuse; there were so many conflicting points of view on display, it was hard to figure out what the message was or what the city stood for, sartorially speaking. Indeed, for a while it seemed that was the message: it’s a global world, there isn’t any metropolitan story. Fair enough. But then something changed.

“I think the rise of high street [fashion] had a lot to do with it,” says Valerie Steele, director and chief curator of the museum at New York’s Fashion Institute of Technology. “Because the whole idea of sportswear got appropriated by fast fashion, so designers had to figure out what their value-added would be. Their first reaction was to make their clothes fancier – more Parisian, if you want – but then they realised: first, during a recession, being experimental is not necessarily the right answer; and, second, if you make your clothes better – better fabrics, construction, raise them to the level of luxury – that is the point of difference. You can’t knock off incredible fabrics.”

Collins agrees. “It is about elevation, as opposed to taking something from high to low” – the flipside of high fashion brands collaborating with the high street.

It is also a response to the straitened economic times, which have created a groundswell of demand among the still-moneyed classes for more discrete, less public luxury: the sort of indulgent garment that speaks to the wearer but not the watcher by dint of its fabrications and fit – which is to say, luxury sportswear. A double-faced cashmere sweatshirt does not look all that different, at first glance, from a regular sweatshirt but its feel and cut adds an extra dimension.

Krakoff, who started his eponymous brand in 2010, says, “I looked at sportswear and thought, ‘As it is, it can’t be done any better, so what can we do next?’”

The answer, it seems, was to combine the building blocks of historical European luxury and the American tradition. Kors, who worked in Paris from 1997 to 2003 as creative director of Céline, says he was very struck during this period by the fact that “for all the French tradition and talk about couture, French women, on a daily basis, dress in separates.” It was knowledge that would inform his own collection.

“If I stand in any of our stores around the world,” says Kors (and he has 321), “I don’t really see a difference between what someone in Brazil wants, and someone in Chicago, and someone in Shanghai.” He believes the emergence of luxury sportswear as an aesthetic was an inevitable effect of sartorial barriers coming down. For decades, he says, if you went to a department store, “designer sportswear” and “couture” would be separated, and clothes sold as “ensembles”. That’s not true any more.

And just as those old boundaries blurred, so did all the rules about price points (it is now almost a point of pride for women to shop the high street and haute couture at the same time) and about what constituted daywear and evening wear. Jenna Lyons, J Crew’s creative director, went to May’s Met Ball, New York’s social event of the season, in a cropped denim jacket and long pink satin skirt. “Today, serious evening gowns often seem very old,” says Steele.

“Clothes are no longer so delineated,” says Krakoff; weekend and office wear have become almost interchangeable. “It’s more a point of view, as opposed to a classification.”

“We think about mobility a lot in terms of our collection,” says Kors. “Here’s a piece: how many different ways can you wear it?”

“People used to be very disparaging about this kind of fashion,” says Collins. “But it takes an enormous amount of confidence to be able to make something that is so apparently simple but, nevertheless, is made from the most extraordinary materials and costs a huge amount of money. And that confidence, in the end, I think of as a very, well, American quality.”