Regarding differences between Canada & USA when it comes to driving, there aren't many, although I think I recall being warned when renting a car in Quebec that turning right on red is not permitted.
The biggest differences I've noted is that the "freeways" in Canada don't quite seem up to Interstate standards (close, but not quite). Examples of what I mean, comparing the 401 to say 1-81 in upstate NY (or any other interstate) are as follows...
a) right shoulder is paved and extends out almost as wide as the width of a lane in the US...in Canada you often get 2 feet of right shoulder then gravel.
b) left shoulder is also wider on interstates than in Canada
c) lanes themselves seem slightly narrower in Canada
d) Cdn mileage signs are not made with high quality "reflector stuff"...you can barely read them at night (at least in Ontario)
There also seems to be fewer of them.
e) some cities have a terribly underdeveloped freeway network...
i) Vancouver is such a beautiful place but has a fundamental flaw....severely difficult to get around in; drives me nuts as a visitor, can't imagine living with that every day!
ii) Edmonton is a wonderful city too but what's with the "bits and pieces" freeway belt around it? ....you think you're fine cruising along then suddenly, here come the traffic lights! Why is there no continuous freeway loop around the city?? Ditto for Calgary!
iii) Toronto before the 407 came along was a total disaster....that freeway was needed 20 years ago (but thankfully it's here now).
Could probably use another "outer" loop (10 -12 miles north of the 407) very soon. By the way, the way the rental car companies deal with the automated toll is a serious rip-off (getting a bill in the mail a few weeks after the fact plus an $8.50 admin fee has got to be one of the worst "let's screw the visitors"
tactics ever!)
iv) Montreal is in a class by itself for confusing roads/dangerous ramps/generally weird highway design
Having said all of this, the drivers in Canada do seem to be generally friendly and laid-back (exception: the speed demons in Quebec).
And, I really love visiting Canada...it's just the roads that irk me(and restaurant food quality) but that's a whole other thread!!!
Happy St Pat's Week!