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.
If confronted at a bar I’d consider it for basically all the reasons you mentioned. When I send updates to my friends in France or Ireland or China I find myself apologizing for wherever embarrassing things we’ve done most recently.
An entire nation has a racist grandad at every dinner