I think that a lot of it isn't country-specific at all. People often just believe that the way they do things is the best way to do those things.
That's not usually a problem in and of itself. A person can believe that a Kosher diet is best and that's OK. It's also OK when a person believes that bacon cheeseburgers are a necessary spice of life.
They can find joy in being spread out over an expansive rural property, with room for some chickens and a whole fleet of cars and to serve dinner to 34 guests on a holiday. A person can also appreciate the rote efficiency of a sleep tube apartment and spend their waking hours not in their own space, but in spaces that are shared with everyone.
It's part of the human condition to have strong opinions. It's often OK that these opinions aren't compatible with eachother. It's good to be tolerant of others' ideas and practices.
It only becomes particularly problematic when folks stop being tolerant and start projecting their opinions onto others. Discourse can devolve pretty quickly when that happens. It can degrade to places well beyond "No true Scotsman" namecalling and invocations of Godwin's law -- whole wars have started over differences of opinion.
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Now, of course, there is are local elements as well. For instance, a person who grew up in Vietnam may have a very different idea of what dinner consists of compared to the ideas of a person who grew up in Guatemala.
Regionalized differences of opinion shows up very often in online discussions because people of cultural different backgrounds get to converse together. It's usually OK. Sometimes, it isn't OK.
A lot of the Web is US-centric, or at least in English. A lot of people in the world speak English as a second language because that's the language that Americans use, so that's what they were taught. The news, worldwide, covers whatever it is the US is doing. And when I went to public school in Ohio [USA], where we were taught over and over again that the US is the very best place on earth and were stand and pledge our allegiance to the flag, and our country, every single morning.
That kind of shit all tends to promote an us-vs-them response on all sides, instead of tolerance and acceptance.
That's not a particularly useful operating mode, but it's what we've got.
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Sometimes, it seems like it's fun to make fun of Americans with their big cars and their dumb flimsy houses made of sticks, paper, and stone dust, with the worst electrical plugs that carry the most uselessly-low voltage. (Those Yanks can't even figure out how to build a proper kettle! Look at them, all driving to Wal-Mart instead of just walking to the shops! Wasting away on the freeway commute when they could be enjoying a nice Schnitzel on the train!)
And since so much of the web is US-centric, it's easy to imagine that people sometimes find themselves surrounded by Americans that they variously find to be unsavory. And if that happens, then it may be the case that they don't like that very much.
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But I don't pop in over to European- and Asian-centric online forums much. When I do, then I don't spend any time at all making fun of their cultural or societal differences.
In fact, I avoid starting that kind of confrontation at every cost. I avoid this simply because I'm not a complete piece of shit.