[nolverostae]

Yes, but now give out the statistics on how much of the calories fed to cows in total in the US or worldwide is actually grazing and how much is from crops that need extra area apart from where the animals graze. Even cattle that grazes is often supplemented with grain, and the grain is of course much more calorie-dense.

The world wide land area for farming would reduce from 4 to 1 billion hectares if we didn't use livestock to feed humans. https://ourworldindata.org/land-use-diets

So the answer to "what would we do with all that land we can't put crops on" is "whatever we want". For example, we could just leave it be nature, since we don't need it for farming.