Those who claim the US benefits by draining the best and the brightest from around the world are doing two things wrong:
1) They bad liars. Everyone knows they just want cheap labor. Just cut the noise already and accept the fact that they may have to send some mangers overseas.
2) Even if they happen to get someone particularly gifted to leave their native land and work cheap in the US, they're ignoring the negative impact this has on those -- usually developing -- economies which need their best and brightest in order to grow their economies to become importers of US goods and services.