Q11. Updated: Are non-U.S. citizens visiting the United States on vacation or for drone competitions required to register?
A. Everyone, including foreign nationals and tourists, who operate a UAS for hobby or recreational purposes outdoors in the U.S. must use the FAA's online registration system. These non-U.S. citizens or non-permanent U.S. residents will receive the same registration certificate as U.S. Citizens or permanent U.S. residents. However, this certificate will function as a "recognition of ownership" document. This document is required by the Department of Transportation for foreign nationals to operate legally in the US.
Q28. Is there a citizenship requirement?
A. Only United States citizens can register their small UAS. The certificate serves as a certificate of ownership for non-citizens, not a registration certificate.
I have seen reference to using a paper system rather than online for foreign registrations - but I've never seen further details.
Perhaps you should just hold off and register online when you get there?