I find it much more likely that Google is merely whining. They're providing an excuse in the form of "not enough AI workers" for getting more cheap imported labor rather than simply hiring and training more expensive, local talent.
Take a look at the current AI landscape in the US. Almost everyone at the top of the field is a first generation immigrant, who managed to make it in while the process was still easy. It's wild that people see the clear benefits of their work to the economy and to US supremacy and then turn around and say that we need to stop importing talent because it takes away domestic jobs.
As for the "what have US colleges been doing" question – take a look at the nationalities of research departments at any major university in the country. The smartest people come here from all over the world to study, and are now promptly sent home with all the knowledge they gained because we don't let them put that knowledge to work here.
Oh right, brain drain is a foreign policy strategy to keep other countries down and America strong. Right, shutting up now.
You are and that realization will eventually hurt.
I want people to succeed - in their home countries. That's fine, let them do that. I'm also a fan of legal immigration - you come here by the book, throw on the jersey, you're on the team. That's fine too. If you don't do that though, I'm not only not a fan but those people shouldn't be here.
If you're a fan of legal immigration, that's great - then certainly you agree that we ought to increase it rather than restrict it.