Buffalo mass shooting - Great Replacement Theory & the long trail of blood

That's an extremely dubious statement to make and one very much more of today's politics than history(just like in the past you'd find the opposite statement made.

It's more complex than that, however the most successful and stable societies in history tended to be quite the opposite of "diverse". When diversity showed up it was pretty much always at the point of a sword. Babylon a good example. It was ruled and fought over by a succession of peoples from the area who were pretty closely related culturally anyway. Egypt was very local Egyptian and when it wasn't it was because of invaders from the south(Kush) or later Greeks and Italians eyeing up the place again at the point of a sword. At the height of her Powers Egypt was local Egyptian.

The Greek city states that gave us so much were even more demographically insular. They could barely tolerate the other city states and saw each other as oddballs never mind non Greek outsiders. The Greek barboros where we get barbarian they applied to anyone who was "other" and a non Greek speaker. When they speak of other cultures and peoples it tends to be of the "ah bless, they think they're people" type of thing.

Rome by dint of being an empire was more "multicultural" alright but very much with an over reaching mother culture that brooked little to no dissent from the "other" and tended to get stabby if the idea of Roman was in danger of being diluted. One reason early Christians were made dietary supplements for lions was because the religion was seen as "Un-Roman". And where they invaded and conquered the natives who "became more Roman than the Romans themselves" as it were became the new middle class and local rulers. Similar setup for the later Islamic empire. Similar setup for the Chinese empire(even today with her 50 ethnicities it's the Han that run the place).

Even in Ireland the vast majority of inward immigration in the last twenty years has been other "White" Europeans. If we add up the Poles, Germans, French, Spanish, British etc that have come here, the vast majority of whom are pale of skin they completely dwarf the African and East Asian demographics.

Personally I don't go by the "White" label. I'd see world populations as very roughly African, IndoEuropean, Asian*. Under the IndoEuropean umbrella I'd include Swedes and Persians and Italians and Indians. The majority of modern Europeans can trace their ancestry back to Middle Eastern farmers. Another factor would be admixtures from archaic humans which also follow these labels. EG Africans have almost no Neandertal DNA, IndoEuropeans have the most, Asians have Neandertal DNA but different sequences and they also have bits of Denisovan DNA, which neither Africans, nor Europeans have.

*The natives of the Americas are an offshoot of north east Asian, though there may have been some Western European in the mix.

If they look like the native population that background fades pretty quickly. A generation at most. If they don't not nearly so much. This is the problem with the multicultural dream and IMHO it is a dream and dreams are nice, but one not born out by reality. You might have a [insert nation here] passport, but if you don't look like you're from [insert nation here] it gets a lot more complex. Look at the UK. The kids of the AfroCaribbean folks who went to the UK in the 40's and 50's were rioting in Brixton in the 1970's because they well knew it was BS. Their kids and grandkids went on BLM marches in the UK because they well know it's BS. British but not quite "British" enough for quite a large percentage of the population. Unless they win medals at sports or hit the Top of The Pops, then they become more "British" alright. Even the pale faced actor Peter O'Toole said that he noticed if he won some acting gong or other he was "British", but if he woke up in the papers for hellraising he became "Irish".