If any good software engineer were allowed carte blanche emigration to the US, the US would have more of the world's top engineering talent, which may be a good thing overall even if it depresses wages. On the other hand, high wages may encourage more young US citizens to go into computer science--assuming they can hack it.
I wonder if this is just another nature vs nurture debate. If you presume that the world's supply of "smart people" is fixed, you want to import all of them and get them to procreate in the US. If you assume intelligence is growable, you want to focus on growing it domestically.