I really doubt that. Surely it can't be uncorrelated with America's pervasive habits of all-day-TV-watching, all-day-computer-use, multi-thousand calorie meals, junk foods, fast foods, car-commuting, and sedentarism?
I didn't say that food quality is the only factor but in my view it plays a role. And I believe a lot of American regular food is very low quality. The things you have listed play a role too.
Well, in France, except for car-commuting, we're going fast gain all those habits.