Bay,
I imported a project from the UK to the US some years ago. The
rules for projects are the same as for completed aircraft. Here's my
understanding.
Only US citizens, permanent residents or US based companies can
own aircraft on the US register. I deregistered the aircraft from the
UK CAA register, but since I came to the US on an H1B I was then unable
to register it with the FAA. This was a probem, because I couldn't get
insurance for the project without an N-number. Fortunately my wife is a
US citizen, so I sold it to her, and it's now registered in her name.
I understand that the rules are the same in Canada, and heard
from an expat over there that the option of registering the aircraft in
the name of a shell company and leasing it back to the temporary
resident is realtively easy and legal.
Costs are minimal, and I got a lot of help, advice and
clarification from the FAA representatives at Sun-n-Fun some years ago.
Regards,