PARIS — As dawn broke in central Paris on Wednesday, a throng of 500 people, mostly French, stood with uncharacteristic patience in a snaking line, intent on buying a decidedly un-French confection: an American doughnut. A hot, glazed Krispy Kreme doughnut, to be exact.

The sight of French people flocking to American fare might have seemed surreal a generation ago in a country that loves its Michelin-starred restaurants, three-hour dinners and iconic baguette. But today, the world’s gastronomic capital happens to be one of the biggest markets in Europe for major American fast-food chains, as evolving consumer habits, influenced by a more casual younger generation and social media, reshape the dining landscape.

In the spring, Popeye’s fried chicken drew huge crowds in Paris when it opened the first of 350 restaurants planned across France. Wendy’s has announced plans to set up shop in France. Burger King, KFC, Starbucks, Domino’s Pizza, Chipotle, Steak ’n Shake, Carl’s Jr. and Five Guys have long had toeholds, but they are rapidly expanding their footprints with plans for hundreds of new locations across the country.

Leading the pack is McDonald’s. After the U.S., France is the chain’s most profitable country.