This is not correct. SpaceX is covered by ITAR and therefore cannot hire foreigners.

Of the approximately 70,000 Tesla employees in the US, fewer than 2,000 are H-1B workers. The rest are US citizens or permanent residents. Tesla's manufacturing is much more vertically integrated than other auto manufacturers, so they rely almost entirely on their US factories to produce the cars they sell in the US. Other auto makers tend to do more manufacturing overseas to save on labor/safety/environmental costs, then do final assembly in the US to avoid tariffs.