Disclaimer: This is not meant to be a bait or any kind of bad-faith devaluing or stereotyping. This is only based on my experience, hearing similar stories from others and wanting to understand. I'm aware that there are good and bad people everywhere.
So I'm European and starting on a good note I always admired America for many things like the freedom, diversity and cool movies.
But after more experience with meeting real Americans I noticed this personality type that I and I think many other non-Americans would describe as arrogant.
Like I stated before I'm not saying every American is like that and I know there are many very nice Americans. But I often saw that some Americans seem to only be nice on the surface (if at all) but actually seem to have this attitude of "I don't give a f about you". And I know that America is a very individualistic culture that focuses on the self and the belief that everyone can achieve anything on their own.
But I still think having a sense of empathy and sensitivity towards others is a very important core human quality that everyone should have. And from personal experience and also from a very prevalent notion of others both in every day life and when looking it up online it's clear that many non-Americans perceive many Americans to cross a line there.
For example there's a prevalent observation of Americans visiting other countries and acting like they own the place by being very loud, demanding and not accepting if things aren't the same way as they are in America.
We know that Americans have very big issues with divisiveness and social injustice and it seams like there's also this sort of "ghetto" personality including trash-talking, lots of vulgar slang and slurs and bragging.
And a general perception of money playing a big role as if many Americans judge someone's worth by money and this attitude of not feeling like needing to help someone. I think there's this famous description of a person lying in the middle of the ground in a public city and people just walk around the person not feeling the need to help.
It almost feels like they're very entitled and put their ego up way higher than it actually is and lacking the quality of making themselves smaller/putting themselves second to treat others with more dignity.
There are good replies here already, but I just want to emphasize the role of bragging. It seems boasting about yourself is quite accepted and sometimes perhaps even expected in the US. In Europe it is not at all, and we tend to react strongly to it.
Whenever I've found Americans to be insufferable they've always been bragging or taking themselves too seriously.
Not all Americans obviously. And I guess a lot of Americans can't stand these people either. But it's still a common American trait that very few Europeans will have patience for. Even our narcissists have learned to pretend to be humble.
Yeah, my mom and I (in the Philippines) saw an American talk about having lots of money quite loudly in a shopping mall. We were put off.
American here. If I was at a mall here in the US and heard this kind of bragging I'd roll my eyes, too.
I was once trying to buy some snacks at a market and a person's card was declined so they started bragging about how much money they had in the bank and that the store was wrong. Everyone just sighed and groaned around her.