This question is meant to be in good faith. I know this topic can be charged but please try to be understanding.
As a 19 year old from Europe I'm just trying to understand why so many Americans (of course not all, but many) not just only seem to have stereotypes against foreigners/immigrants with different nationality such as Mexicans etc. (which is also the case here in Europe), but also exclude and stereotype other Americans solely based on their looks (or what many Americans call "race").
For example I think many people in Europe unfortunately also are racist against immigrants and people with nationality from a different country because they fear that they're bringing crime and drastically change the culture (because many of them are Muslims etc. and have very different world views and might not accept ours). In America this seems to be the case as well emphasizing "American values"/"America first" and excluding everything that's against that and mass deporting immigrants.
But what's even harder for me to understand is why so many Americans seem to exclude and racially stereotype other Americans solely based on their appearance that has nothing to do with their personality. They could have the exact same personality, interests, religion, same number of American ancestors etc. but still separate and stereotype each other based on their skin or face appearance.
Of course this also exists in Europe but it seems way more rare than in America. In American culture it seems like it has normalized that people constantly talk about skin color (being "black" or "white") and other "races" that they exclude and stereotype. Like calling people "black people" or "white people" as if they're a different species.
For example France also has many people with dark skin and other features but they seem to be way more integrated and mixed. If it's racist they're mostly related to someones nationality or personality but not whether how dark or pale their skin is or whether they look Asian.
For example I have friends with dark skin but we never talk about that. We might only talk about it the same way we talk about having different hair and eye color but we don't obsess over it as if we're different people because of that.
It would seem very weird here if someone said "I don't date Asians". Or things like "Black-Only" Schools or communities would be unthinkable here.
The act of calling someone "black" or "white" alone seems weird imo, since skin color isn't truly "black" or "white" like coal and paper are. Imo it's more like a brown/orange/pink color that varies in darkness between people but there's no distinct point where someone is considered dark/black or pale/white anyways.
And to me it always seemed completely normal that all humans naturally look different, some more some less (which I think is a more healthy and realistic view).
I know America has a long racist history but that doesn't justify this imo and seems weird to still take place in 2025.
I wanted to add that even though I believe that there's probably still a lot of the discrimination against our own people in some places of Europe that you mentioned, I have to say that I rarely experience this.
Like the example you gave for the UK, even though I have never lived there for a long period, I've been there many times and I've never seen anyone mentioning the societal class. Maybe from movies or games that play in the past they say "Look at this poor peasant" but I've never experienced this IRL.
I don't wanna hate on America at all (I think it's an awesome country in many ways), I think this is just important constructive criticism because I've experienced so many times that Americans called people black or white and made a stereotyping/discriminating thing out of it, said the N word etc.
And especially for purely appearance based reasons I think it's particularly bad because no one can change their body or skin color since that's how they were born.
But of course we need to get rid of all discrimination including the ones against foreigners that Europe also definitely has!