https://www.ers.usda.gov/amber-waves/2024/december/ers-data-...
and
https://www.ers.usda.gov/topics/crops/corn-and-other-feed-gr...
Let me surface a more direct article: https://insideanimalag.org/land-use-for-animal-ag/#:~:text=1...
Of the total land area of the contiguous 48 states, ~45% is used for animal ag. This includes: Land for grazing livestock at ~35%. Land for crops going specifically to animal feed at ~9%. Animal ag farmsteads at <1%.[1-3]
So yes, most cows are eating grass like a wandering herd.
Most cows do eat grass and other stuff we can't eat.
"Hard feed" is made from crops grown as part of a rotation cycle, or from things like soya where 80% of it is only suitable for cattle feed.
Citations please.
When i looked into internet [1] it says "approximately 95% of the cattle in the United States continue to be finished, or fattened, on grain"