Are you saying that you can tell the difference between a Canadian accent and an American one? I'm not sure I believe it. (I mean, I can see you being able to tell the difference between a Toronto accent and a Brooklyn accent, say, because frankly everyone can (though they might not know that that is what they are) but a general US/CAN average accent?
I'm from Vancouver, and while visiting Japan, I met some Americans who said, "You're Canadian? But you have no accent!", to which I responded "You're just saying that because I sound like people on TV. That's because most people you see on TV are from Vancouver."
It's an exaggeration with some small truth to it.