It's a fact(I guess?) that they are that percentage of farmworkers. It's not a fact that without them that farms would not survive in America.
https://www.npr.org/sections/thesalt/2018/07/31/634442195/wh...
We already can't find enough labor:
https://www.latimes.com/projects/la-fi-farm-labor-guestworke...
and unemployment is historically very low.
Is your argument that if we kicked every illegal immigrant out of America tomorrow, that Americans would just choose to starve instead of paying slightly more for food, and farmers would just let food rot on the vine instead of harvesting it?
Oh, they wouldn't choose. They'd just have that as the inevitable consequence. Famines happen; just wishing them away isn't really a great approach.
It doesn't help that these decisions take months/years to show their impacts.
In this scenario, some farmer is going to choose to pay $20/hr for farm workers, and rake in insane profits if there really is a famine. In fact, almost all farms would choose to pay more to collect their food and sell it at a large premium in the case of a food shortage.
And hope that in six months, the trade war hasn't been settled? They won't be paid until the crop matures, and there's a lot of labor before that point. You're also competing with other countries, from whom we already import agricultural goods at reasonable prices.
Again, decisions that lead to famine don't do so instantly.
https://en.wikipedia.org/wiki/Onion_Futures_Act
You're full of easy solutions to tough problems, aren't you?