Um... what? This is ludicrous, bordering on insane.
Tone down the hyperbole
By this view the United States would have had massive internal conflicts throughout its history
It did and still does. I suggest refreshing your understanding of American history. The US suppressed most of these conflicts via Western cultural dominance and strict government controls. The US government tried incredibly hard to break up cultural "pockets" and disperse them within the US in order to prevent them from retaining their cultural identity beyond the first generation. The US education system was designed based on achieving this, taking notes from what they did to the native Americans. The US was diverse on paper, but it only managed it through extremely intense integration programs which worked. those programs largely dissolved the cultural foundations of immigrants in favor of American culture. Diversity doesn't mean eating tacos on Tuesday and watching anime. Diversity goes way, way, way deeper than that. Talk to a person born in China, Saudi Arabia, or Chad. Their entire world view would be different than yours. If you asked them what makes a country, they'd answer differently than you.
Also, the US wasn't truly multicultural at this time. It largely limited immigration to culturally-similar Western cultures. It was incredibly picky about non-Western Europeans. For the most part, it didn't let them in unless it was going to use them as highly exploited labor. For most of it's history, the US had a de facto policy of maintaining it's Western cultural protestant roots. One of the reasons why it was very spiteful towards Italians and Irish during certain periods.
You simply don't notice these thingsbecause US culture and zeitgeist is the dominant global regime since WWII. It has spread it's immigrant culture to countries that largely didn't have histories of this. Most of "modernity" is just an extension of American cultural dominance and hegemony. Not unlike the British before it. The current age is the most totalitarian ever in human history. More aspects of your life are controlled and managed than any other period by miles. And the very second that tight control and trust in the powers-at-be wavers, people will come into conflict because they have nothing else to guide or rely on unless they have a strong communal structure as a social safety net. Do I really need to point out that is happening now?
Also, it is important to realize the US is a historical aberration. And a young one at that. It is an on going experiment that nobody knows the final result of.
while Russia would have been a beacon of stability.
Russia is incredibly diverse. It is also low density empire. I have no idea what point you are making here. The only thing that keeps Russia together is repression. Without that, it would fracture into cultural and ethnic pockets.
I don't think there's any real evidence that more culturally-based countries have fewer internal conflicts.
Then you simply don't know history at all. Like, at all. There is a direct correlation between social stability and diversity. People keep making the mistake of extending the aberrant period of 1945-2020 as being an eternal state of progress when it clearly isn't. History operates in cycles, not a line going up. We are currently living in the end of one that started in the early 20th century. And that is the same reason why everyone acts like history started with WWII. Because in a way, it did. The worldview most Westerners ascribe to was born from WWII's ashes.
And quite frankly, the West at the moment are akin to a traumatized person who hasn't quite admitted to themselves that they are traumatized yet. WWII was immensely socially traumatizing to much of the world. Not just the West. And many of our beliefs stem from that trauma, not reality.
Look at how poorly many modern homogenous European nations deal with large immigration waves
Mistaking cause with effect. It was only after European countries started dissolving their cultural identity that they started to decline. But I'm not going to have this discussion because it will get this thread locked. Also, most european countries are far from homogenous. Japan is homogenous. France is not. UK is not.
But I'll say this. What made Europe strong was that it was it was a collection of highly competitive group of different ethnicities and cultures. That distinction and competition spawned innovation and progress. Europe's attempt at broad unity, erasing cultural differences, and breaking down the concept of people has only harmed it. Competition stimulating growth isn't just a capitalist concept. Lack of competition is also why so many Chinese dynasties stagnated.
I can't see how that's a case that multiculturalism is any increase to social upheaval and internal conflict
The entire foundation of a nation (or the antiquity equivalent) is it's people. It's people must have a shared history, identity, and core set of beliefs and view of reality. Their zeitgeist. If you force together large numbers of people with little to nothing in common, then conflict WILL arise because the needs, wants, beliefs, and desires of the people will all be different. One of the reason so many Americans feel so lonely, empty, and lack community is specifically because their collective identity is so incredibly weak. So they try and fill the void with consumerism instead. Most Americans don't even know their own history.
Stable societies can only exist when their is a general identity unifying them. One of the number one ways empires conquered people was by watering them down. Romans flooded recently conquered regions with Italians. China floods the Uyghurs with Chinese. The US broke up native tribes and mixed them in with colonials.
When you break up peoples collective identities, roots, and sense of belonging they weaken relative to those in power. However, if that is done to all of society, then society rips itself apart the section authorities aren't forcing everyone to live together.
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Right now you are just repeating the zeitgeist you were taught and born into, not the reality of how humanity operates and civilizations form.
