The distinction is becoming more and more arbitrary. A century ago, the distinction was clear: France has a time-honored canon of regional specialties—pot au feu, coq au vin, quiche Lorraine, cassoulet, navarin d’agneau, etc.—that are considered to have been so polished by repetition as to be immutable national treasures. For a very long time, French cooks just did their best to interpret these classics to the best of their ability, like a conductor trying to do right by Beethoven.
Then came Escoffier. He was one of the first megastars of French cuisine. He essentially codified the exact way every dish—no, every element of every dish—was to be prepared. His versions were seen for most of the following century as the definitive expression of French cuisine; the unimprovable standard.
Nouvelle Cuisine, a movement originating among a handful of chefs in Lyon in the 70s, basically threw away Escofier with his rich, heavy, over-the-top preparations, and instituted a minimalist approach using light, lean, concentrated flavors. From this point on, the French-ness of French cuisine became more elusive, since every chef was given free rein to invent without being bound by precedent.