I think you may find a lot of folks from other countries are being trained or checked out in the GOM to fly for U.S. companies that are diversified in other countries. Not necessarily working in the states.
Also when some of the new guys get an initial VISA to do training its good for a certain period. They can work on that VISA until it expires. Listen to the Radios as there are many accents now working in the states.
Those that I have met are pretty good folks, Welcome....