I have to say yes. Not that it’s really fair to get angry at someone who mistakes me for an American, but I would correct them.
It could literally be dangerous to not correct them in some foreign countries (ones I would avoid if at all possible, but still).
I get so offended I offer only the curtest of apologies for causing their confusion.
I just listen for the eh, eh?
That one has an element of truth, but it’s not nearly as common as the stereotypes make it out to be. There was an interview with a homeowner on TV the other day about a truck accident on his property, and it was like “I just saw this truck coming up the road, eh? And before I knew it, it went right through my fence, eh?” and so on and so on. I just burst out laughing, it was like a Bob and Doug McKenzie skit without the Molson Ex. Most people don’t normally talk like that, except the types who also for some reason have to end every sentence with “right?” or “you know what I’m sayin’?”. What is, however, true is that Canadians are more likely to say “eh?” as an expression of confusion where an American would say “huh?”.
We do? I’m a 60 yr old Canadian and I don’t know anyone who pronounces it that way.
The “leftenant” thing’s interesting though. I retired as a Canadian naval lt (Lt(N) in Cdn). Brits pronounce it “leftenant” as well. I don’t know for sure but I suspect the Brit pronunciation is the result of a historical antipathy to France, whereas France was an ally to the early US.
Ah, okay! Thought maybe there was a variant I hadn’t noticed before. 
Maybe it was the Molson Ex that made the guy drive through the fence, eh?
When I was working with Ford, at one point I was shuttling between the plant in Windsor and the HQ in Dearborn. The manager I was working with subtly shifted his speech patterns every time we crossed the Ambassador Bridge. Not a lot, but enough that I could tell there was a difference.
No, no and, uh, no.
Schedule is skedule, Lieutenant is lieutenant and about is about. Other than on TV, I’ve never ever heard anyone say shedule, or leftenant (and I was in the army) or aboot. The latter being something I stick on my foot. Nor do I say out ‘oot’ because I’m not an owl.
It is different, though, in a lot of Canadian accents. Like I said, it’s not “aboot,” closer to something like “aboat,” but not quite–it’s a bit subtler, but it sticks out to me so much that I’ll be listening to a Youtuber or NPR commentator and when it comes up I’m like, oh, that’s Canadian.
The “shedule” thing is something I only hear on CBC radio, and even there it seems to be falling slightly out of fashion.
And we Canadians tend to not like Americans wearing Canadian flags abroad… 
With regards to about, it’s a thing called Canadian raising.
Canadians have a hard time grasping this because Americans seem to be suggesting that we pronounce the second vowel in ‘about’ as a single vowel rather than a dipthong (and argue about whether it’s more aboot or aboat), when it is clearly a dipthong to Canadian ears.
For Canadians, consider how you say the words ‘lout’ and ‘loud’. Same vowel? Not for most of us. ‘Loud’ is more dipthongy, as it were. When the ‘ou’ dipthong appears before a voiceless consonant like ‘t’ it is shifted slightly, starting at a different place than when it precedes a voiced consonant like ‘d’. In most American dialects this doesn’t happen, and ‘lout’ (and ‘about’) have exactly the same vowel as in ‘loud’ or ‘crowd’.
For Americans, it may or may not help to consider another form of raising (depending on your dialect). Consider the vowels in ‘ride’, ‘side’, and ‘prize’ vs the vowels in ‘light’, ‘sight’, and ‘price’. In some American dialects, and most Canadian, the latter group of vowels are raised in a similar fashion to the Canadian ‘about’.
Sorry, you’re absolutely wrong about the pronunciation of Lt. How long were you in the army (and whose army?) and which regiment? I was in a strictly naval environment for 15 years and then various tri-service units for 15. I’ve never heard "loo"tenant except when dealing with American and other non-commonwealth officers.
Funny, your name is my ‘tell’ for Canadians.
Fargo took place in Baja Canada.
Offended? Of course not. It’s an easy mistake to make. Most of us sound like your typical mid-west, Johnny Carson type accents.
There is a subtle difference in “about” but it certainly isn’t “aboot.”
Lieutenant is ALWAYS “leftenant.”
I don’t pronounce the “t” in “often.”
One other subtlety not mentioned is the pasta/Mazda thing. Canadians pronounce both the vowel sounds the same way, like you’d pronounce Santa. Americans say something like “pawsta” and “Mawzda.”
So, no, not offended at all, but will correct if required.
Obviously you’ve never listened to NHL hockey broadcasts. Canadian announcers reveal their origin within 30 seconds on average.
Catch this episode of Forensic Files sometime. It’s a classic eh-fest.
One of my very dear friends is Portuguese by way of Canada. That’s to say she was born in Portugal but is a Canadian citizen and was raised there. It’s comical how she can’t tell how pronounced her aboots are either. Some of you protesting may not be able to hear it as clearly as we do. She also doesn’t realize she says eh. And she does. A lot.
Link to the Forensic Files “Bad Blood” episode (3 "eh"s from three separate participants within 20 seconds beginning at the 4:40 mark).
They’re from Saskatchewan, if that makes a difference.
No, we all do in fact say “eh” a lot. I have to catch myself when I’m in the US because the speech pattern is very much ingrained in us.