Dera,
There can be many reasons for getting FAA license without having the right to work in the US.
I recently did my FAA ticket, based on my EASA ATPL, because it gives me/the company, added flexibility in choosing simulator providers for initials/re-currents. Lot's of corporate/private jet management companies manages airframes registered in The Cayman's, Bermuda etc and they would validate an FAA license.
Secondly I believe there are a lot of N reg.'s around the world, that you can work on with an FAA license, without having the right to live/work on US soil.
Cheers,
K.