Heres the thing I don’t think there ever has been a unified American culture, as soon as assholes started to step off this boats there was already inevitable cultural divergences happening, for example the Massachusetts Puritans who were theocratically driven, the Marylanders who were driven by proto-secular ideals, and Valirginians who were economically driven. While the Mid-Atlandit and New England cultures did reconverge over the last century of so, Coastal Southern especially the rural variants is still noticeably divergent from the rest of the east coast.

Also I’m just gonna note that everything you listed is caused by top down economic pressures that are arguably on the verge of collapse. One of the things you have to factor into your analysis of American cultures is that all of them are subject to federal level pressures meaning that even the most communal cultures for example still have to participate in capitalism due to say taxes since that’s basically the only way to earn cash. I suspect once the feds collapse you’ll see a springtime of nations and the possible death of the Pan American amalgam culture, at least within the first 20 years or so.

america is also composed of spanish irish italian black dutch native American german asian culture to name a few

While that may be true it’s very much in the same way that Roman culture is the basis and founding of Modern Romantic cultures. It’s to degrees and the more derived and hybridized the individual cultures are the more distant they become, not even accounting for cultural drift by time alone.

But I will also note that I don’t think the US has a united culture and what is often seen as a Pan American culture is moreso a side effect of the post World Wars migration, the migrations of the great depression/dust bowl, and the yuppies migrating about creating a rough amalgam culture that often out populates the older more divergent regional cultures. Basically if you think of a cultureless suburbanite that’s the thing I’m talking about. Also I think mass media reinforced the whole thing.

The foundational European culture of California is Spanish.

While language influences culture and culture influences language they are not the same by any means. Plus within the last hundred years the US has become increasingly mono-lingual in favor of English, according to my great great aunt for example when she was a little girl her father would still speak to himself in a German dialect because German was his first language since he was from a German town. A lot of these minority languages have either naturally due to trade or whatnot or via force from the feds been on the decline or are now extinct some of which predated the founding of the US. A similar thing happened with a lot of regional dialects.

Also define so called high culture? Because frankly given how much of Europe once shared a Greco-Roman high culture irrespective of their own regional cultures I’m gonna call that a potential irrelevancy.