Hello Mike:

I have vague recollections of this being a nuisance when I tried doing it when I was a resident of New York for work purposes starting in the late '90s. At the time I had a Ford, and I recall that there were two main things that needed to be addressed, the Federal Motor Vehicle Safety Standard (FMVSS) and the Environmental Protection Agency requirements (EPA). The FMVSS stuff was pretty hard and fast (lighting, seat belts, bumpers), the EPA stuff was weird-- involving having the car undercarriage pressure washed so that it wouldn't harbor pathogens.

I ended up baling on the whole idea, leaving the Ford for my fiancee who was still a resident of Ontario. I just bought a US car (that's when I got into Volvos!).

In the US system there are registered motor vehicle importers-- there used to be a list online that you could download. Good luck!
--
Herb Goltz, London, Ontario, Canada '92 245 w/109K mi