by and large the definition of “white” has been pretty stable for a couple hundred years at least
That's not really true. Italians weren't exactly considered white at the top of the 20th century, Irish not long before that, and not too much longer before that anyone anywhere near the Mediterranean wasn't considered white.
This is a common "mostly truth" that gets passed around a lot but is missing pieces. Italians were considered white as they were qualified for (lower tiered) entry as US citizens before the 1870 Naturalization act and weren't actually targeted in things like anti-miscegenation laws like Indians and Japanese were (with famous cases), but with key points of nuance:
There was a hierarchy of numerous white "races". You had "Nordics" at the top while Southern Italians, Irishmen, Slavs, and Jews at the bottom, but occupying their own creative "niche". This isn't to say there weren't "ambiguous" cases like Hungarians, Caucasians, Finns, and Turks but now they are all, save Turks, pretty much accepted aside from the racist fringe.
"White" and "Native" occupied the same cultural space. So when nativists were yammering about True Americans and "good white people" getting screwed over by the immigrants, they meant WASPs and everyone else (especially ethnicities associated with Catholics and, at the turn of the century, anarchists/socialists like with Sacco and Vanzetti).
There were certainly "popular" theories that caught on during times of race science and eugenics, like the Italians and Irish sharing ancestry with Africans or Russians sharing ancestry with Asians (Sound familiar?) and whatnot, but the extent of which this caught on with the general populace and for how long is debatable.
This contradicts the myth of Pan-European harmony that most modern day white nationalists and fascists like to paint of American history with, but it doesn't dismiss entirely that there was some consistent (if arbitrary) basis for what was considered "white". European immigrants have the advantage of being able to blend in easier than African or Asian Americans, which seems to be the ticket. European Jews occupy an "interesting" place in that while they can blend in just as well, the historic antisemitism combined with a perceived "non-European" origin makes them especially hated by white supremacists who view them as deceitful infiltrators.
In general, I think mainstream white supremacy has largely been replaced with an "American" identity with white supremacist undertones and inert castes, and that will only continue with demographics going the way they are as America's settler-colonial nature isn't going away. For less-mainstream white supremacists (fascists), there's already a schism happening between explicit white supremacists and implicitly racist "Western" supremacists, like with the Proud Boys.
That's not really true. Italians weren't exactly considered white at the top of the 20th century, Irish not long before that, and not too much longer before that anyone anywhere near the Mediterranean wasn't considered white.
This is a common "mostly truth" that gets passed around a lot but is missing pieces. Italians were considered white as they were qualified for (lower tiered) entry as US citizens before the 1870 Naturalization act and weren't actually targeted in things like anti-miscegenation laws like Indians and Japanese were (with famous cases), but with key points of nuance:
There was a hierarchy of numerous white "races". You had "Nordics" at the top while Southern Italians, Irishmen, Slavs, and Jews at the bottom, but occupying their own creative "niche". This isn't to say there weren't "ambiguous" cases like Hungarians, Caucasians, Finns, and Turks but now they are all, save Turks, pretty much accepted aside from the racist fringe.
"White" and "Native" occupied the same cultural space. So when nativists were yammering about True Americans and "good white people" getting screwed over by the immigrants, they meant WASPs and everyone else (especially ethnicities associated with Catholics and, at the turn of the century, anarchists/socialists like with Sacco and Vanzetti).
There were certainly "popular" theories that caught on during times of race science and eugenics, like the Italians and Irish sharing ancestry with Africans or Russians sharing ancestry with Asians (Sound familiar?) and whatnot, but the extent of which this caught on with the general populace and for how long is debatable.
This contradicts the myth of Pan-European harmony that most modern day white nationalists and fascists like to paint of American history with, but it doesn't dismiss entirely that there was some consistent (if arbitrary) basis for what was considered "white". European immigrants have the advantage of being able to blend in easier than African or Asian Americans, which seems to be the ticket. European Jews occupy an "interesting" place in that while they can blend in just as well, the historic antisemitism combined with a perceived "non-European" origin makes them especially hated by white supremacists who view them as deceitful infiltrators.
In general, I think mainstream white supremacy has largely been replaced with an "American" identity with white supremacist undertones and inert castes, and that will only continue with demographics going the way they are as America's settler-colonial nature isn't going away. For less-mainstream white supremacists (fascists), there's already a schism happening between explicit white supremacists and implicitly racist "Western" supremacists, like with the Proud Boys.