Great question, I've often wondered about the same thing. I think it's probably a combination of factors, the most important being, in my view, culture. I sus

Great question, I've often wondered about the same thing. I think it's probably a combination of factors, the most important being, in my view, culture. I suspect that other countries may have more homogeneous eating traditions than the U.S. If most people around you are eating the same sorts of foods, and eating occupies the same space in their lives, its probably less likely to occur to you to go buy a bag of fritos or a pizza or something. If everyone around you is behaving in varied ways with respect to food, you may be more likely to make decisions based on price, convenience, or the "food buzz" you get from eating something. It may also be that buying everything based on price and convenience is itself a cultural norm in the U.S. It might be economic factors as well. If the U.S. is the world leader in corn production and industrial-scale agriculture, the market for food products in the U.S. might just be very different from what exists in Europe. Finally there is the possibility that the U.S is not alone in the obesity epidemic, merely ahead. I'm not totally sold on that, but it's a possibility.