Years ago, during the Vietnam War, border guards used a shibboleth test to identify Americans who were going north to escape the draft. Some of the sentences were these:
I have taken the wrong route.
I am neither juvenile nor hostile.
My house needs a new roof.
There were a bunch more.
I read about this in a book called Canadian Raising, which is a great read if you're interested in this stuff.
Another difference is /or/ words like sorry, tomorrow, borrow, and the like. Canadians tend to pronounce these as a pure oh sounds whereas Americans make a ah sound. "Sorry" in American sounds like something an Indian lady would wear. ;-)