I recently did some research on it because a lot of Canadian aircraft pop up for sale and aren't very far away from me in Minnesota. I was looking at an EAB Super Cub and started digging into what it would take. While it is a pain in the ass, it's not terrible as far as those go.
Some things I know:
1. You have to connect with a DAR who possesses the codes to grant an airworthiness certificate for EAB. This can be different from the DAR who possesses the codes to perform a conformity inspection on a certified aircraft prior to granting a normal category AW cert. It's best if this person is near your home base because there's waiting involved.
2. Getting the aircraft to your home base can be tough, as on the northern side of the border, the pilot must possess a Canadian pilot certificate to pilot a C-number aircraft in country. And once it crosses into the US, it must also be piloted by a Canadian pilot certificate. Basically a US pilot certificate can't pilot the C-numbered aircraft, unless you have gotten your
US "licence" validated by TC.
3. The FAA is big on having the aircraft deregistered from the TC registry prior to allowing a registration application.
4. Applying for the Experimental airworthiness certificate is essentially like starting from scratch as if you had built one.
5. Following that, the FAA will require some evidence of amateur build. There's a form/document that can be requested from TC that essentially says "yeah this aircraft was granted an experimental AW cert here in Canada and that builder supplied the requisite documentation at the time" but I'm not sure how hard that is to get. And build evidence may get lost in the shuffle of time and multiple owners on the Canada side.
6. It would make the most sense to use an escrow of some kind where to condition of successful conversion to US AW cert must be met for the sale, but if I was a Canadian aircraft owner I'd prob not roll the dice. It seems like a roll of the dice on both sides.
Hopefully someone here can correct any of my erroneous info or provide more clarity.