I don't think that this issue is specific to the food service sector. I think the reason healthy food is hard to find in America is the same reason that the only way to have a healthy social ecosystem online is to painstakingly develop it at a grassroots level: corporate interests have taken over. The second that a corporate entity takes hold, growth is made the only priority and the system will naturally develop insidious patterns which abuse our most pathological tendencies. Let's refactor your comment using social media:
> Isn’t it strange how the only way to have a meaningful discussion on the internet is to spend hours researching and filtering through a sea of clickbait/porn/fakenews/gossip?
> Every social media website is unhealthy. Most well-known forums are unhealthy.
I think the unfortunate reality is that we will continue to slip into these patterns until we stop responding to them. It's a self-perpetuating cycle. We all need to strive to find out what healthy means and crawl towards that. Unfortunately things will continue to spiral out of control to the degree they need to for us to change, and sadly some people will be lost along the way.
Other possibilities:
* Food is now abundant. The whole idea of healthy food is relatively new. Only the very rich used to be overweight, but now even the poorest can afford enough food to become obese
* American food is heavy and fatty as a matter of tradition. Burgers, fries, fast food are all cultural artifacts most commonly associated with the US.
* Multiple generations of Americans have been raised in front of the television and have deep seeded emotional imprinting from fast food marketing (happy meals!)