Will use this as issue for the enhancement of removing "race" as cultural separator in the mod - with some special exceptions when race is denominates race based voting blocks like in the US. North America too could get a cultural identity, seeing as by the point North America gets any sort of political union it'd realistically be an ethnic ball-pit- perhaps "Americano"? It has a nice feel to it for starters, and while Mexicans aren't gonna take over the USA they could realistically influence American English with those sorts of quirks like Germans and Yiddish did. I think ASEAN would make a new cultural identity as a part of the "ASEAN way" descision, and while it would be Malay-influenced I don't see Indonesian being anything more than an accepted culture. Also potentially the Pacific Islands Federation and Latin America, because I don't see a need for a new common identity emerging there). I'd also definitely support union cultural groups, except in the various Muslim-world Unions and Eurasia (which would be a bit less integrative and mixy-mashy culturally and more ethnically-conscious, I imagine. These minority racial cultures could also exist in the UK, and have an option to become accepted cultures as soon as London became a white minority city IRL. Maybe even an assimilated MENA culture for these countries. Why don't we assimilate immigrants into their own race-based cultural groups? For instance, Chinese, Koreans and Viets could become "Asian Anglo", Nigerians and other Africans could become "Black Anglo", Indians and Pakistanis could become "Subcontinental" and Mestizos/White Spanish could become "Hispanic" when in an anglo country like Australia and the USA. I have an idea for the Americas and Oceania. One could have new super state identities that have higher assimilation rates (like European for EU, maybe mestizo for the Americas, the different black linguistic cultures for Africa).
This is difficult to mod in Vic2, so I don't know how to solve it. Some even took pride in having Punic origin - Carthage the old mortal enemy of Old Rome - showing a merge of identities). eventually non of the emperor where old latin. And those Romans did not correlate to the old "latin tribes" that initially build the empire but pops how had been assimilated into the empire (Philip the Arab, the Illyrian Emperors. What is happening today seems to be what happens in old imperial Rome - tribes eventually where assimilated into a new imperial language based identity of Romans and Greeks.
In Britain immigrants are much more likely to be "British" than English and more likely to be pro EU than (local)nationalist. Maybe reality is something along the lines pops tend to only marginally assimilate into local old world cultures - instead what happens is an assimilation into something else - a new common identity (a statist identity, think about superstates like the EU).