Most human beings don't come close to maximizing the realization of their potential. And many of the countries that are the biggest sources of immigrants to the United States have very much of a "growth mindset"
http://www.stanfordalumni.org/news/magazine/2007/marapr/feat...
in general in their cultures, and particularly in the subcultures that supply most of the immigrants to the United States, such that those immigrants, whatever their IQ scores, do more to realize their potential than people with "fixed mindset." Indeed, there is a whole book on this subject, James R. Flynn's Asian Americans: Achievement Beyond IQ.
http://www.amazon.com/Asian-Americans-Achievement-Beyond-Iq/...
The IQ threshold for eminent achievement and even "genius" (as carefully defined by psychologists) is not particularly high, but is only about 120 on a currently normed IQ test. That, by definition of IQ standard scoring, is less than two standard deviations above the population mean.
Follow-up comments to this by request.
Note that Flynn (yes, that one) is no racist.