"And, we will have done a remarkable thing. While underdeveloped nations like China and India are making progress toward prosperity, we, as the most powerful economy in world history, will driven ourselves into third world poverty."
How do you think India and China are doing it? Certainly not through central planning or through restriction of the labor supply. If we're really intent on saving our primary sector, larger quantities of cheap labor are exactly what we need.
We do not need more cheap labor. Wages have already declined substantially in low-wage occupations. Check the research by Borjas, Briggs, etc.
And by the way, illegal alien labor is massively subsidized.