The only constant is that nobody seems content just taking the upper hand of keeping their stereotypes to themselves. Everyone acts like they've lived 5 years in every country and somehow know how it all crumbles. In reality maybe they've lived in two countries and have had day-visits elsewhere. Hardly grounds for being a master of the nations.
Like someone swearing that <some city> drivers are the worst. Almost guaranteed that they grew up there.
American tourists didn't even have a bad rap where I worked in Prague because you just didn't see them compared to the daily horde of Europeans. By the time you work in the hospitality industry for a few seasonal cycles, you get burned out by the exact same conversations, like people arguing over which nation tourists suck the most. Turns out it's probably just the one you see the most of. In our case, the British. ;)
These days it's on HN where people will post the template: "I took a few day trip to <place> and it's insane how <judgmental thing that people seem to do everywhere>."
Full restaurants in Italy are a deafening cacophony. It's an arms race amongst people already accustomed to yelling at eachother on a daily basis.