Editing to be more substantive: America's food culture is really terrible. We take 'celebration' foods from other cultures and then eat them like it's normal food. For one example, tamales used to be a Sunday or Christmas only thing, but now you get tamales any time you like.
Also, corporations are there to make a profit, so if they can sell you a nothing burger, they will. It's really easy to make high calorie, high flavor foods, and it's also really easy to sell that food.
---
As an aside, I've been going to physical therapy for my ankle, and a lady from Scotland was next to me one day - she said she gained 15 pounds in a couple months after moving to Texas from Scotland - and not from fast food.