Well that's all fair and well, but would you be willing to accept the tripling, quadrupling or even quintupling of price in groceries that would come from that?
If you replace every single immigrant "slave" with a fairly paid American(but do note what "American" actually means, it includes all of South America and all of North America and stretches from Chile to Canada), If you'd pay US wages for every single of those that'd dramatically increase the price of the wares that those people produce because it's not like you'd see any real increase in productivity and they're going to pass the price increase off to the end customer.
It's either that or making US citizens work for the same slave wages that the immigrants do, and boy would that result in unions and strikes...