This walling off of the affluent, of whom I was a part, was something I really noticed in Houston TX during my 2 years there. Neighbourhoods seemed to have a cliff edge. The fact nobody walked did not help. Cars can be a terrible curse in creating social isolation and stratification. One never met someone from a poor neighbourhood in the street or at the supermarket. (By the way, there were vanishingly few inter-racial couples to be seen, compared to Europe.) There was also a shocking tendency among some of my neighbours to speak disparagingly about poor people "trailer trash" etc, which I found very jarring. Paradoxically, this went alongside a degree of charitable giving that exceeded what I was used to in Britain. I never quite worked it out.
There are a lot of cities like that to some degree. It's somewhat different where I'm at, as it's kind of a patch of blue in a red state (but turning purple), but there are also gated communities here as well. "Trailer trash" is a disparaging term which I've heard quite a bit. On the other hand, I've encountered people on the streets for whom moving into a trailer would be an improvement. Some people have to live in tents, and they're becoming more and more visible across the country.
In London, one of the nice features is that you get blocks of council housing for the poor, right in the middle of rich areas. This has to be a good thing, both for reminding the rich how the other half lives - and not least that they are human beings just like them - and for allowing the poor to enjoy tree-lined, clean streets, and decent shops and public transport.
There are panhandlers around here who often stand on street corners carrying signs. Sometimes they stand on the medians at intersections. So, even people in cars passing by see them every day. They're also pretty common in front of convenience stores and various other shops. In some cases, they seem pretty messed up, like they've got some sort of drug/alcohol or other mental problem - and probably could benefit from some sort of treatment, if any were available (the current system is somewhat overloaded, understaffed, and underfunded).
Some regions and cities seem to have more of a blue-collar/working class vibe about them, and there's sometimes a general feeling of "we're all in the same boat." But in the cities which seem more focused on the glamourous lifestyles of the rich and famous tend to be more divided and somewhat more cold-blooded about things.
So, some of the stratification in the cities seems to be playing out at a national and regional level. A local politician or business manager might say "Well, we'd like to help, but it's not our fault. It's the bigwigs at the state capital or corporate headquarters or the executives on Wall Street or those danged liberals in Washington. They're the ones who are the problem." That's what the folks down in Podunk are hearing. That's the kind of talk that puts them in a blaming kind of mood.
One big difference across the Atlantic is that in Europe many of the rich feel some sense of responsibility towards the poor, sometimes even guilt for their advantages. They are aware from history that the playing field was never level, that wealth begets more wealth etc, and so a sense of noblesse oblige remains in society. In the US my sense is that the American Dream is that everyone starts level and has equal opportunities if they are only willing to grasp them. So if they don't do well it's their own fault. This a myth of course - but a very convenient one for the affluent.
On various levels, the rise of liberalism and progressivism happened in the US on par with Europe, as both Teddy Roosevelt and Woodrow Wilson started to recognize the need for better conditions ("The New Nationalism" and "The New Freedom"). FDR moved even further in that direction with "The New Deal." This was how the tide was turned from the half-century of Republican rule after the Civil War. (Wilson was kind of an odd bird, as he was kind of a liberal and even thought he could achieve a lasting world peace, yet still had that Dixiecrat racist attitude. That's where the Dixiecrats hit a bit of a tangle which changed the Democratic Party irrevocably.)
No doubt times were still hard back then, and when the Depression hit, it got even worse. World War was a major game-changer, as the US had to marshal its resources and dramatically increase industrial production, while Europe and East Asia laid in ruins. Our industries remained untouched, so we were in a favorable position for a while, and, even while Republicans screamed about communist plots everywhere, the post-war dividend also brought about great improvements, not just in terms of people's individual incomes and living standards, but also in the country overall. The interstate highway system and many other great public works came about. The leisure/consumerist society was born. Labor unions were also much stronger back then, so workers could get fair contracts and earn a decent wage, enough to support a family in the suburbs, which also boomed.
Of course, all of this fed quite nicely into the ideals encapsulated in the "American Dream." LBJ continued with his "Great Society" program and the "War on Poverty," although his main problem was in Vietnam. That's what led us to Nixon, and that's probably when things started to go awry. Then we got Reagan, and that's the point when things really went downhill. That's when Trump started to become popular, as he was symbolic of that era. The character of Gordon Gekko in the movie Wall Street also falls into that mold. It wasn't really the same "American Dream," anymore, or it somehow corporatized or turned into some kind of political gimmick more than anything truly real or genuine. It was also the rise of the Moral Majority, which was neither. (I was part of the Immoral Minority myself.)