So how many cars are made and sold only in Canada?
Not many I guess, so they will all comply with harmonised standards and over read.
The Canadian rules require a little more than there must be a means of indicating speed to the driver, it must be illuninated when the lights are on, must be MPH or KPH (or both) and must be labled to say which.
Inerestingly the European rules now say the speedometer must be indepenent i.e. a GPS speedometer is not acceptable. I assume so you can't say "sorry officer the GPS dropped out" when speeding.