Two points to make here.
1) Canadian vehicle standards are identical to US standards and the VIN label the manufacture makes can state that the vehicle meets the standards for both countries.
2) Don’t get confused between Federal and State requirements. Many people have registered vehicles with their State that do not meet Federal standards, but that does not make them legal. It still leaves the owner open to liability, and it still leaves the owner open to having their coverage cancelled. Bringing anything into the US is regulated by the Federal government and it’s not over as far as they are concerned just because you managed to register the vehicle.
I will have to dig it up, but I found something saying if approved for use in Canada, its go to go for import into the States.