As a Brit with FAA licenses, I am stuck between volunteering my pilot/instructor time in the UK/EU (cannot earn without EASA licenses) and the same in the US (visa requirement).
I have focused on ground school and there is a small niche in defence where the civilian regulator does not exist. It gets to me that EASA schools can operate in the US with non-qualified (only validated) personnel, and the reverse is not allowed.