I have heard people talk about how absurd individuals like Ben Shapiro could still find an audience is because they help a lot of people explain away racism. So why many Americans refuse to acknowledge racism still exist? I mean, if they feels guilty about it, then just say something not unlike "There is no ethical consumption under capitalism.", then be a do-nothing purely-rhetorical reformist.
Or, in another world, why racists don't like to be called racist? I know that there have been people who were fired after it came out that they were bigots. But realistically, what is the possible negative outcome your average American racist can expect? They are forced to move to Missisipi?
the short answer is that people don't like to think they are the bad guy so they don't think they're being racist is the short answer. They react defensively when you "insult" them by calling them racist from their pov.
The longer answer is that american culture is embedded with white supremacy, to the point where it's not even immediately visible to white people to see how racist every single blood soaked part of the history and mechanics of this country is. People then justify their learned cultural racism as "everyone's a little bit racist" or "but [stereotype] is true because [subjective experience]!" etc etc. There's also the part where the libs did that fun little trick they did where they act like any past progress was amazing, great, should be celebrated (even though they hated it at the time) but it's the maximum limit. So then you get the "but black people can vote/we had obama as president" like that solved structural racism. And of course there is 0 education on any sort of black history or issues in school so people literally just do not confront their racism and then get defensive when forced too.
One issue imo is that the liberal conception of racism is so individualistic, and any accusation of racist behavior becomes a character judgement against the accused person, causing them to lash out. This is often appropriate of course. It does make it difficult to conceptualize though, since radlibs still fall back on "understanding why I'm part of the problem" [if white] even if they love to call it "systemic" (which would mean treating racism as a social construct that both enables and results from other exploitative social constructs, rather than just a bunch of bad people who are being bad)