Most US workers, even if young and healthy, would make it maybe 1/2 day harvesting crops, and would likely be flat on their back in intense pain for days later. We have as a society largely forgotten how to do this kind of hard labor. I lived in a border farming community for 3 years with nearly 30% unemployment, lots of farm jobs and only the Mexicans and Central Americans willing to do the work. They would work long hours stooped over picking lettuce in the hot sun every day without complaint, happy for the work. The US farm industry would be destroyed without their help, and they will certainly not be replaced by displaced older white workers.