I've only ever done it the other way around. US to Canada.
FWIW,
I had to verify that the vehicle could be imported through our Registrar of Vehicles. They have a list of what can and can't be imported to Canada from the USA. Towables and motorized RVs.
Then I had to get a statement of clear title and a bill of sale from the seller.
Then it had to be checked for recalls - certified by the manufacturer as having had everything done, or that there weren't any recalls.
Then it had to be insured - had to get temporary coverage through a Canadian insurer of RVs - I think it was good for 2 weeks?
Then it had to be physically imported through a port of exit/entry (US/Canadian border) and if it was a motorized RV, it had to be inspected by CBP prior to exiting the US. This required prior notification to CBP that it was on it's way out of the country, and the inspection could take more than 24 hours depending on how busy they were. I had to make an appointment, effectively with 4 days lead time, IIRC?
Then on the Canadian side (after release by CBP) I had to pay the first half of the taxes (Federal GST 5%) at the CBSA customs on our side and they checked all the paperwork, and issued a temporary pass/registration and a notice that it had to be inspected by a registered agent of the RIV (see above) that it was the vehicle in the paperwork (serial/VIN number) and that it was compliant with all of our Federal CSA standards for the vehicle type. If anything wasn't compliant, it had to be modified to make it compliant.
Then once that was done and I received the "all clear" I had to take the paperwork to my provincial vehicle registration offices to get a registration certificate and pay the 2nd tax (provincial sales tax 8%) to get a license plate.
Simple?
Mike. Comments are anecdotal or personal opinions, and worth what you paid for them.
2018 (2017 Sprinter Cab Chassis) Navion24V + 2016 Wrangler JKU (sold @ ????)
2016 Sunstar 26HE, V10, 3V, 6 Speed (sold @ 4600 miles)
2002 Roadtrek C190P (sold @ 315,000kms)