Americans eat so much processed food simply because it is much cheaper than fresh food. Processed food is made to get consumers addicted (through convenience, taste, etc.) and encourage them to consume much more. Fresh food is almost the opposite.
I grew up in a country where freshly made food is actually cheaper than processed food, even to this day. People who stick to a traditional diet are mostly thin, while those who stick to a processed food diet gain a lot of weight.
I don't understand how people come to this conclusion
Beans/grains/legumes are cheap
Frozen veg is dirt cheap (and retains its nutrition as good as, or better than fresh). In-season fruit and veg
Which foods are more expensive?
People are door-dashing their salaries away and complaining about the price of fresh food...
Convenience and addiction makes more sense, certainly not price
Then maybe you shouldn't speak on it until you understand how they came to this conclusion. Knowing you have opinions based on ignorance and refusing to change isn't a good way to live.
Put another way: it doesn't make sense for people to come to that conclusion because it's so obviously wrong if they actually check prices
I then give examples