PARIS — Nothing says Parisian chic like a tractor jacket.

Forget the nipped blazers, the custom loafers, the cleverly knotted Hermès cravats. Get yourself to the Carhartt outpost here, a short walk from Colette, the retailing madhouse where, at a recently installed Balenciaga pop-up shop, one can order a T-shirt customized with logos as tacky as the ones at a stall next to a saltwater taffy stand in Atlantic City. Printed on site, they cost a mere 255 euros (about $285).

Follow the men’s wear shows in Florence, Milan and Paris for three weeks and what you’ll notice is, of all things, America already is first. Stealthily, the sportswear that is a mostly American innovation has become a universalized form of millennial dress.

It turns up in the sneakers from almost every luxury goods house and in the tricked-out tracksuits, car coats and gym shoes that overshadowed the few traditional wardrobe elements in the new Valentino collection.