That whole concept of "Jobs Americans Wont Do" is precisely one of those phrases.
Humm, wonder why we_aren't_doing_those_jobs?
Not all Americans have the physical ability or stamina to keep up with the average agricultural worker.
The work itself is hard physical labor, similar to the building construction. The Prevailing Wage in most states for construction trades is $30.00/hr and up. That is approximately what you would have to pay to get skilled US ag workers to put in an eight hour day. Did you know US citizens know and demand their Rights? Think they are going to move 7 times a year and live in a non A/C hut like sardines? Uh, maybe 60-70$ per diem living expense plus travel expense.
Here is what it boils down to,
US citizen payroll and expenses 300-350$/8hrs plus travel Illegal contract 80-100$/12 hrs
I have done some hobby farming. One of my customers had run a crew of Mexicans at their behest. He is pushing 70 now and still turns out a good days work. I've know him a few years. He told me he could not keep up with their pace, 12 hour days, rain or shine, pesticides, snakes whatever. They made good money by their standards.
He became friends with them. They need a "straw boss", to negotiate with the land owners, local authorities in English. Often the "straw boss" is a contract labor provider and take a disproportionate share of the(ir) monies.