As an American who has traveled a lot, I think a large part of the problem here is Americans’ over reliance on restaurants for food. You can rightly criticize the processed, sugary, or fried foods that many people habitually cook, but to claim that Americans don’t know how to make plain foods or have access to the ingredients is ignorance: every proper grocery store sells good proteins, fresh vegetables, and unprocessed grains, and they do it because it’s profitable, because people do largely cook pretty standard meals at home (and as others noted, your yogurt example is wrong). But regardless of how healthy our cooking is, why is it so rare for Americans to eat a home cooked lunch, and so strikingly common to meet people who never cook their own dinner when compared to other countries? Your country has on average healthier foods than we do (not sure by how much once you account for the dishes people actually order), but the portions at restaurants are still too big. People are healthier in France because they cook most of their meals at home, not because the restaurants give them a proper diet. If we all started eating like the French do we’d probably have a more balanced diet, but we’d still be fat if we ate at restaurants all the time.