Things may be tough enough for a lot of American retail chains, but maybe that's the best time for foreign invaders to strike. British retail sensation Topshop is invading our shores as we speak, having already launched a U.S. e-commerce website as it plans for its first U.S. store (in New York), which is set to debut in the next couple months.

There has been a lot of buzz about Topshop -- owned by privately held Arcadia Group -- prior to its official U.S. arrival. It's a player in what's known as the "fast fashion" category, which also includes Spain's Zara, Sweden's H&M (OTC BB: HMRZF.PK), as well as Forever 21 and Charlotte Russe (NASDAQ:CHIC).

These companies come out with high-fashion pieces with lightning speed, at low or medium price points. Shoppers often snap up the limited-quantity goods, and the quick turnover of items encourages them to stop in frequently. These retailers are adept at nimble turnaround and some choose to manufacture apparel close to home to save time to market. Talk about a wake-up call for less nimble fashion retailers across the board.

Topshop has a Kate Moss line to speak for it, too; the supermodel is a business partner with Topshop head Sir Philip Green. (Similarly, H&M has had collections linked to celebrities like Madonna and Stella McCartney.)  

This wouldn't be the first time a "British invasion" could be perceived as a competitive challenge for American retailers. Britain's Tesco's small-scale encroachment onto U.S. soil has been viewed as possibly significant for retailers as different from one another as Wal-Mart and Whole Foods Market (NASDAQ:WFMI); both have experimented with small, nimble stores, possibly at least partly in response to Tesco's entry.

A single U.S. store for Topshop -- albeit in a U.S. fashion mecca -- may not seem like a big deal in the retail landscape, but I think the website is, since many fashion-minded American women have probably been waiting eagerly for Topshop. This could prove a competitive challenge not only to similar retailers, but also to hip retailers like Urban Outfitters (NASDAQ:URBN), American Apparel (NYSE:APP), and Target (NYSE:TGT). (On the other end of the spectrum, maybe the landscape looks even more depressing for perennial strugglers like Gap (NYSE:GPS)).

It looks to me like many fashion retailers duking it out in the U.S. -- especially for increasingly fickle shoppers in these difficult economic times -- have one more reason to really focus on getting on top of their game.

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Alyce Lomax owns shares of Urban Outfitters and Whole Foods Market. The Fool has a disclosure policy.