Have you spent time in rural or poor areas or the US? Try eating the local food. It's not good. As an american who moved abroad, I can say american food is just shockingly low quality. High fat and/or high sugar, lots of highly processed food. Very common attitude that "I have never and will never like vegetables". I mean I'd expect some people live off a diet like sugary cereal, soda, milk, wonder bread, mac and cheese, mayo, ground beef, eggs, candy, fries, pizza, etc. Keep in mind the most common vegetable that americans eat is the potato.

That being said, it is absolutely not the individuals fault for being obese. I'm convinced there are effects that are hormonal, chemical polutants, or epigenetics that push the population to being fatter. The lack of education, and knowledge of how people live in other parts of the world does not help either.