Take someone with a good work ethic from anywhere on this globe, be he/she Mexican, Chinese, African, Arab, or European, and they and/or their children will do just fine here in the United States - no matter what their genetic makeup is.
Which is why, of course, IQ is the best predictor of future income than any other variable.
If you have an IQ under 100, I don't care how hard you work. You're just not going to become a brilliant scientist. Of course, there people with IQ's over 150 who don't amount to anything. That just means IQ is a necessary but not sufficient condition for intellectual success.