There is no greater critic of US cuisine than the French. Our foods and tastes are almost polar opposite than that of the French. To place an American grocery store in the country could prove to be offensive to them and may not be very successful outside of local ex-patriots.
Even the most uncultured eater knows that French cuisine is rich, complex, and very, very fancy. American Cuisine? Not so much. But don’t underestimate the appeal of a hearty, American meal: the ingredients dehydrated, measured out for you, and stuffed in a tidy little box with instructions. Instant oatmeal, Heinz ketchup, and the fixings for Buffalo wings can all be obtained here, and Parisians and tourists alike flock to the American grocery every time they get a hankering.
When people travel or they live away from home, they like to have access to their comfort food. How man Chinese or Mexican or other International stores and restaurants are there in the United States? And people love them. People in France should embrace diversity and welcome an American store. It's just for the people who want to shop there.
In the United States, we have ordinary American grocery chains, but there are also Mexican grocery stores, Indian grocery stores, Middle Eastern grocery stores, etc. I love that about the U.S. Having a variety of food options and a variety of cultures and groups of people is a beautiful thing. French people should embrace diversity and appreciate having more options.