I just went through this process (took about 4 months). Glad to have a chance to pay it forward. If you'll message me, I can send you my number.
short version:
1. Need Transport Canada CofA for Export performed by TC Ministry Delegate (with export authority-- not all MD's have it)
2. Need FAA CofA performed by FAA DAR-T.
Prerequisites for 1 are:
a. Full annual within 30 days of the M.D.'s inspection for 1.
b. As part of the annual, a conformance inspection, performed by a certified shop/ mechanic attesting to the fact that the aircraft conforms to the Type certificate. It was blurry in terms of the distinction between "a" and "b," but "b" involved getting paperwork prepared related to all STC's.
Prerequisites for 2:
a. Plane needs to be registered in US before step 2. And a pre-req for FAA registration is proof of deregistration from Transport Canada.
b. 100 hour inspection (or annual) by FAA A&P, within 30 days of DAR-T's inspection. the annual in Canada can't count for this. This also entails documenting all STC's for the DAR-T's review. (which means transcribing the Canadian STC's from step 1b onto form 337).
c. Once 2a and 2b are completed, you are ready for the DAR-T's visit and sign-off.
Summary: when you're finished, notwithstanding whether the plane needed an annual, you will have done two full annuals, because of the 30-day timing requirements on each end. The actual Officials involved (The TC MD and the FAA DAR-T) took just one day each. It's all the supportive stuff that takes time.
Other notes: Whether the aircraft was manufactured in the US originally may impact the process slightly, but I don't think it allows you to skip any of the steps above. There's something called the "bilateral agreement" (from NAFTA & its successor) that's supposed to make this process as listed simpler than if coming from another country. (e.g. the attestation done in Canada is w/r/t to the FAA Type Certiciate)