I know that apparently, some American travelers put Canadian flags on their luggage or carry on then claiming they’re from Canada (the dead giveaway on debunking this is their passport, since how can you be “Canadian” when you have US citizenship unless you’re a dual citizen in possession of both nationalities) since some of them have hatred towards the US or feel ashamed of the country due to its internal affairs.
I remember meeting some masquerading Americans during the Iraq war. These were backpackers in SE Asia.
You only show your passport at the border or maybe when you get a car or a hotel room. That leaves a lot of time to pretend being Canadian everywhere else.
That being said, I just saw a comedy bit where this was recommended to Americans. I think it’s more meme than happening IRL today.
american dad did an episode, where they pretended to be canadians just to fit in internaitonally.
There was also a Simpsons scene (from the George W. Bush administration) where Lisa did that.
Immediately followed by Homer making a scene about being an American