>>16773179 (OP)
The US has 340 million people. If it needs to brain drain other countries, that's an indictment of the US's ability to develop its own people. There never should be any need to import any time of labor or specialist from outside with a pool of people that large. Even if you subtract out the 55 million visa holders, 15 million green card holders, and 50 million illegals, you still end up with over 200 million. Develop what you have instead of demanding quick fixes by raiding other countries for their talent base.