Not surprisingly, the population of STEM graduate programs is vastly dominated by foreign students. "81 percent of full-time graduate students in electrical and petroleum engineering programs at U.S. universities are international students, and 79 percent in computer science are."

https://www.insidehighered.com/quicktakes/2017/10/11/foreign...

That is more because a grad degree is a unnecessary expense for an American who wants an industry job, so the only Americans who go for grad degrees are people who want to be in academia. A masters contains a lot of repeated information from a bachelors, and many masters programs from "reputable" schools are now diploma mills that prey on international students willingness to pay large amounts of money an American degree.

Advanced degrees also make getting certain visas easier. The relative value for spending money and two years on a Masters or six years of your life on a PhD is much higher if it carries with it a ticket to stay in the U.S.

I was going to say the same thing. Immigration into the US is extremely difficult if you aren't already famous/wealthy/well-connected, that if you want a visa, coming in through education is your best bet. And getting a job with a company that will sponsor your visa (to say nothing of one that will sponsor your potential green card) is already difficult, but being a student and having a graduate degree is a good incentive.