Let me ask you a question. Just how many trucks do you forsee going south from the U.S. into Mexico, when U.S. wages will be anywhere from three to five times higher? It seems a given to me than unless U.S. wages dropped by 60 to 80%, that no U.S. trucks would be hired to go into Mexico.
The problem that you keep doing is looking at this from the perspective of truckers instead of what the overall benefit of shifting to areas of more efficiency will be to Americans as a whole.
Loading and unloading a truck at the border is highly inefficient. I think that Americans could drive in Mexico even given the wage differential. The condition of Mexican roads and insurance cost seem to be larger barriers than labor rates.