I have seen it first hand when Indian and other Asian gangs get into companies. In a few months all the Americans are gone.
Americans not being smart enough? Nonsense. The best programmmers I know or have known are Americans. Next best or comparable are Europeans or Russians.
The American programmers I have known are typically the most creative, but least disciplined. Indian programmers are far better for being on time, following design guidelines, documentation, etc.
That's my experience, at least. (And I'm an American programmer...)
Americans not being smart enough?
Who claimed that?