The issue with the Mexican and most Central American economies is graft and corruption at the Governmental level.
As if those things don't exist in the US....
Not even CLOSE to the same level as in Mexico, or Guatemala. Or other Central American countries. The level of corruption we have is nowhere near the same. If that's central to your point - then there's nothing else to discuss.
As for encouraging the immigrants home countries to institute change is exactly what I suggested. You have to help them build their economies which in turn will spur changes. Right now the US trade policies are anything but helpful or friendly.
OK, so how do you propose to do that? We have completely free trade, should we pay them to export their products to us? You have a nice little sound-bite, but what do suggest as action to make it "work"?