Why does the U.S. need to depend on the ~80.000 odd first order immigrants per year to generate that amount of wealth. Couldn't the U.S. somehow draw those ambitious out of its current population?
What if people could 'emigrate' from Detroit to California? They'd basically be refugees from a low-opportunity environment as well.
Or is it not the fact that they came from a low-opportunity environment, but rather that they came like Bill Gates from the tender love and care of rich/succesful parents, and being born abroad was just a small hurdle?