Aircraft can be brought into the US and be made airworthy by FAA standards. What about aircraft legally modified in other countries? For example, there is a new STC to put a Rotax 912 into Cessna 150s approved by the EASA. Can that STC be made legal in the US even though no similar STC exists here? If yes, is this just due to relations between the EASA and FAA, or can this be done with aircraft coming from anywhere?