There are 65k H1-B visas issued every year. The FAANG all have offices in Europe so they can put grads to work there until the visa comes through. Of course some companies are ramping up their dev capacity in Europe due to the shortage of grads in the US, that's why Facebook announced thousands of the devs they're hiring for the Metaverse will be in Europe.
Many people come over on an L1 visa. A U.S. company will higher a foreign worker, have them work in a foreign office for one year, and then they qualify for an L1 visa.
