> Isn't it well known that the main reason that most foreigners have advanced degrees is because that's how they get into the country legally in the first place?

Yes, and ...?

I mean, if it were a requirement to start a business and employ 10 Americans gainfully, would you go and say "Yeah, but the reason so many foreign born people do that is so they can get in legally."

So?

As long as they have higher level training than most Americans, and as long as we spend money training them (via research/teaching grants), isn't it a good idea to keep them?

You're assuming people are really learning anything in those programs that they wouldn't have had in their undergrad. I've never met an American with an undergrad who is underperforming compared to their foreign MS counterparts. The MS is merely a cheaper tool to get into the country than other investment visas plus you get credentialed. I think it's also a bit of a validation tool that the person actually has studied at the same level as US counterparts. I have met some people from India who were surprised at how difficult college was when they came to the US compared to back in India.

> I've never met an American with an undergrad who is underperforming compared to their foreign MS counterparts.

Outside of SW, not many engineering jobs have a mix of undergrads and MS folks doing the same work, so your sample is extremely biased.

> I have met some people from India who were surprised at how difficult college was when they came to the US compared to back in India.

And I've met the opposite. Ask folks who went to the top IITs.

I was surprised at how easy college was in India when I saw the coursework.