It seems to be a major issue with a lot of people here. Plenty of threads such as this one descend into arguments over whether Europe is more diverse culturally than the US. Well here’s a thread for people to debate it.
Disclaimer - I have no great credentials to argue it, I’m not a cultural expert. I’ve been in the United States 6 times, have visited parts of 12 different states, from long stays to a few hours here and there. Other than the Republic of Ireland, I’ve been in the UK (NI, Scotland and England, not really Wales), France, Germany, Spain, Malta, and Italy. I’ve been in the Midwest, the Northeast and the South (barely) US.
Although I have seen diversity amongst the states I’ve visited it, it seems to me that much of the (Eastern at least) US is made up of suburban tracts that don’t huge differ hugely from one another, culturally. This is partly due to the fact that as a visitor one can only spend so much time in any area, one never gets to know all that many people on any but a superficial level, one mightn’t get to know the history of an area etc. Generally speaking, Midwestern culture(s) that I encountered were more introspective, people on the East Coast seemed that bit more international in mindset, but having said that, this was just a general impression and could be just confirmation bias etc. etc.
Linguistically, although many languages other than English are spoken across the US, most prominently Spanish, English is the lingua franca of the country, the mother tongue of the majority and I’ve not (yet) been in a situation in the US where only knowing English was a hindrance. In Europe, most individual nation states have a national language that differs somewhat from their neighbours. Ireland where the lingua franca is English also has the Irish language which forms an important part of the culture, in some very visible ways. Although many people across Europe are educated in English and a tourist may get by speaking English it is easy enough to find oneself in a situation wherein nobody you encounter can speak English, or to the level at which you can meaningfully communicate with them. This has happened to me in Spain and in Italy.
Accent. Anglophone accents vary enough that it is easy enough for many people with the knowledge in Britain and Ireland to identify the town or region a person grew up in. It might not sound that remarkable but it is fairly easy for me to identify someone from a town 10 miles away by their accent, and 10 further miles etc. I don’t have a complete knowledge of all Irish accents but they differ enough from one another as to be specific geographic locators. I’ve heard a surfeit of US accents but they don’t seem to vary with nearly the same frequency as in Ireland but then to my foreign ears I probably miss some of the subtleties. FWIW university educated younger people from across much of the US seem to have a somewhat homogenefied (is that word?) accent.
Ok these are only a couple of things, and cultures are more than these so please feel free to contribute your opinion, points, etc, on either side and let’s please try to keep things civil.
To put it more succinctly, in my experience at least, Europe seems more diverse than the United States, culturally. However, I’ve provided ample caveats about the limits of my exposure.