I think there's a great deal of truth to what you say, especially the idea that most of these issues never really went away. However, I've noticed that they've taken different forms over the course of my lifetime.
Speaking from my own perspective, I was born in 1963. My grandparents were born in the late 19th/early 20th centuries. My parents were born in the 1930s. My grandparents and their generation would have seen a racist society most of their lives.
My parents came of age during the 1950s, when U.S. policy started to shift away from racism and segregation. Some could argue that the reasons for this shift included WW2, when the world saw the extremist nationalism and racism of Nazi Germany which went way beyond the pale. It could be said that, by witnessing such horrific atrocities as committed by the Nazis, it drove the point home just how horrible and malignant such ideas are so as to generate an even stronger reaction against them here in the U.S.
Another reason might be attributable to the Cold War and the fact that the eyes of the world were now upon the U.S. as the premiere superpower and guardian of freedom and democracy. So, with so much light upon America after WW2, things like the Jim Crow laws and other racist policies couldn't simply be ignored, dismissed, or swept under the rug. The world was watching, particularly areas of the world where the U.S. was attempting to gain hearts and minds, as European colonialism left a sour taste in the mouths of many in Africa and Asia, while the Soviet Union reminded them of how they've been treated by Western imperialists and racists. For some Americans, it was just plain embarrassing that President Eisenhower had to formally apologize because a restaurant in Maryland refused to give service to the ambassador from Ghana because of his race. Things like that had to be addressed, and they couldn't be ignored or put on the back burner.
As a result, during the 50s and 60s, there were more protests and attention paid to the matter of civil rights. The media were becoming more sympathetic, and young progressives like JFK and RFK spoke out very strongly against racism and injustice in our society. The military had already been integrated by Truman, and the Supreme Court overturned the precedent of "Separate But Equal" which had been the law since the Civil War. Sports were also becoming integrated, and people of color were becoming more prevalent on TV, radio, and in the music industry. Moreover, popular white performers had crossed over, much to the chagrin of racists who railed against the likes of Elvis Presley and Buddy Holly. Even earlier, blues and jazz became more and more popular, which were the primary influencers of rock and roll which grew near and dear to many Americans.
Of course, the same period was dominated by the politics of the Cold War and the ongoing red scare mentality that existed across America, so that also complicated things. The Civil Rights movement and Anti-War movement were considered suspect, and many of its supporters were accused of being communists or commie sympathizers (pinkos). On the other hand, America's working class and the standard of living across the country had been improving by leaps and bounds. Unions were stronger, and the government and ruling class had an enormous stake in making sure they had the loyalty and support of the American body politic. Their obsession over communism drove them to make capitalism appear as wonderful as possible (see Nixon-Khrushchev Kitchen Debate), as well as pushed them to build up our military forces and challenge communist uprisings wherever and whenever they occurred. This is how we ended up in places like Vietnam in the first place.
The U.S. also had an underground, illicit love affair with organized crime, which started in the 1920s during the Prohibition era, and has continued to the present day. It's become a part of Americana, as illustrated by the popularity of movies such as The Godfather and Goodfellas. This also fed in to our obsession with anti-communism, since communists opposed the Mafia gaining a foothold in places like Cuba.
But it was clear by the mid to late 1960s that the public overwhelmingly supported the Civil Rights Act and the Civil Rights movement in general. LBJ's War on Poverty was immensely popular, although his War against Vietnam was not. This is where the Democrats failed politically, and the party all but imploded at the '68 Convention (which was also marred by RFK's assassination that same year). This cleared the way for Nixon to enter office.
It's also interesting to compare how Americans might have viewed race or people of color during the 20s and 30s versus the 60s and 70s. Stereotypes of black people changed from the inept, dull-witted Stepin Fechit to something more like the Blaxploitation films which were popularized during the 1970s. Blacks were no longer portrayed as harmless or hapless, but instead were transformed into streetwise, angry, and out for revenge. A popular trope in movies and TV would have a white guy with a flat tire or broken down car in a black neighborhood, where he would be invariably hassled or attacked by gangs of young tough blacks. This imagery, while viewed as "hip" at the time, probably contributed to the negative perceptions which would persist. This was also coupled with the major crime waves which occurred from the 70s, though the 80s, and into the 90s.
Even if the politics might have officially supported civil rights and anti-racism, it seems clear that the media were driven towards portraying Blacks and Hispanics as dangerous gang-bangers, agitators, or otherwise angry people - and that white people would be wise to stay away from them and out of their neighborhoods. This also coinciding with the demographic phenomenon known as "white flight," since whites were persuaded to be afraid, but they couldn't publicly express their fears out of a compounded fear of being branded as racist. The rise of political correctness managed to subvert the debate and inhibit public discussions, so many of these issues festered for quite some time.
Meanwhile, new generations were coming of age, people who weren't even born yet and never saw the Civil Rights era, nor did they have any first-hand experience with what America was like before that.
I also wouldn't dismiss the influence of identity politics on the whole situation. I recall a case where a white college student observed the existence of a "Black Students Association" on her campus, so she wanted to start a "White Students Association," yet was told that it was racist to do so. So, the question came up: How come blacks get to do it but whites can't? That's when the whole issue of "white privilege" and the notion that "only whites can be racist" came on the scene, and this is the point where it, sadly, jumped the shark. They would have been far better off to prohibit any associations based on race, rather than come up with weak, convoluted, specious explanations for having a double-standard. This is where it all went wrong, about 30 or so years ago.
Meanwhile, the attitudes you're mentioning continued to fester and grow, with the new technology of the internet coming on the scene. What you're seeing now is dissatisfaction from the lower classes who have grown disaffected and angst-ridden, feeling as if they've been put upon and blamed for things they didn't even do - just because of their skin color, an accident of birth. I don't think most of them would actively embrace racism or nationalism, but there's no other political faction that will listen or even comes close to echoing their viewpoint. The best solution would have been for the Powers That Be to continue the same economic boom which dominated the 50s and 60s. The economic growth rate should have continued unabated. At least, that would pacify the masses, but the capitalists refuse to make the economy better.
So, we have a situation where nearly half the population is living from paycheck to paycheck, being pressured by high prices and gaslighted by dishonest pundits and politicians. The people deserve a break, and if they don't get it soon, there will be hell to pay. It's as simple as that.
This also ties in to the whole problem, because Americans continue to embrace capitalism and its predatory, dog-eat-dog philosophy. It's social Darwinism, the belief that only the strong shall survive.
So, under the current prevailing philosophy which even Democrats and liberals support (by supporting both capitalism and identity politics), these are two things which are evident:
1. It's okay to believe in a predatory, dog-eat-dog philosophy where only the strong, skilled, and wealthy dominate the weak, unskilled, and poor. (Democrats believe this, too, since they support capitalism, although they don't seem to understand that this is the same philosophy as nationalism.)
2. It's okay to categorize and identify with one's race and ancestry.
These two political principles have remained sacrosanct for decades, even in the eyes of liberals. Did they seriously believe that they could pick and choose which groups of people are allowed to believe in these things and which ones weren't? Why would they embrace such beliefs if they didn't think they were good beliefs? Why would they be surprised that other people believe the exact same thing?
The way I see it, this is the price we pay for wanting to have our cake and eat it, too. This is the consequence of inconsistently applied principles. Either you believe in a set of principles or you don't.
If you believe that racism and nationalism are wrong, then you must also say that capitalism and identity politics are equally wrong. If you don't, then don't be surprised if racism and nationalism never go away. You can't have one without the other.
