Trying to credit America's success on the "US Way" is fallacious - I don't think we'd be much worse off if we were ruled by a monarchy, or even an extremely ethnically homogenous culture, since we're protected by two oceans, have massive oil and mineral and forest reserves, and had the native population decimated by infectious diseases before we moved in.

You can't ascribe the position of the US solely to its immigration policies. Especially since it's impossible to correlate immigration trends in recent years in the US to economic trends.