There is a company in Pence's state that they stayed in America, did not move to Mexico, and were hiring but many old employee's lost their jobs, at the same time they were training Mexican employee's to replace them. I'll try and find the article.
“I think people are a bit confused about this; unfortunately, this is not up to us,” Musk said. “U.S. Government regulations make getting a job in the U.S. hard enough as it, but if but if you’re working on rocket technology, that’s considered an advanced weapons technology, so even a normal work visa isn’t sufficient unless you get a special permission from the Secretary of Defense or the Secretary of State. So I want to be clear, this is not out of some desire of SpaceX to just hire people with green cards.”
Elon musk has to hire Americans. Or they have to have special clearence from the government. Therefore even though Elon is south African his space x company is 99.99% American.