[Nyororin]

I think it can be summed up something like this;

There is a slight difference between a Canadian accent and a standard American accent. The difference is present in small parts of speech. (Not evident in all parts of speech.) It is usually clear that it is not a standard American accent - however, it is not identifying as a Canadian accent.

I would say that most people would probably be able to point out that it isn`t a standard American accent if they heard the pronunciations that are different than the standard, but NOT be able to point out where the speaker was from. Both because the accent isn`t Canadian only (overlaps into the US), and because the difference is so slight that it normally wouldn`t stand out enough to draw attention. In a situation where the native accent of the listener is VERY different from the standard, they may not really notice a difference at all - only that the accent is different from their local one, and close to the standard.

There is a MUCH larger difference between most regional accents in the US and the standard than between the Canadian accent and the standard. Because of the huge variety in the US itself, I think it would be pretty strange for someone to assume that such a tiny difference in accent would indicate that someone is from outside the US.

An added note on "Standard American English" - there really is no such thing in everyday use. Announcers all play down their regional accents and also often affect their speech to sound "warmer" and more "friendly" (this is particularly true of news programming). They all strive for the "standard", but there is no location where "standard" American English is actually spoken by the majority of the population. Every location will have some kind of difference when compared to the television standard. I think this is why it is so hard to look at the Canadian accent as a distinct accent - the amount it differs from the standard is so low that it is likely lower than most of the English spoken in the US itself.