I have dealt with Asia a bit, but not Canada.
My guess would be that Canadien Benzs would be US Versions and no modifications would be necessary other than maybe if you are moving to California, where the emmisions are tougher.
I do not think that there is an additional sales tax in addition to the state tax that you would pay, but not sure.
It also depends what year your cars you are selling, if older, may not be even tested for emmisions, if newer, you'd have to pass your state emissions.
I would assume that the only major difference is that your speedometer may read in KM in large numbers???
Would like to hear comments>>>>
'89 420 SEL
'90 300 SEL
'68 Olds 88 Convertible
'84 300 SD (sold it)