It's pretty easy to understand the American mindset once you wrap your head around the notion that all of the freedoms and rights that we love to tout were only really made possible because the extermination of natives and enslavement of blacks provided such a surplus of resources to white men that a lot of the ethnic and class conflicts that had marked their lives back in Europe were suddenly rendered irrelevant. In America, even the humblest peasant, provided he was white of course, could come over and claim a chunk of free land with plenty of free labor to work it, and live like a king with all of the associated rights and privileges that only the nobility would've enjoyed back in the old country. Over the last 50 years so, we've tried to rectify this hypocrisy by trying to extend those same rights to everyone and not just the privileged few that they were intended for, but without a disenfranchised underclass to extract wealth from, all of that sweet talk of liberty and justice hasn't really been able to manifest in reality.
Racism won't disappear just by convincing racists to be better people, because racist policies provided tangible benefits to them and it is simply in their best interest to do whatever it takes to preserve those benefits, ideals of equality be damned. Our only real options here are to either pay them off, which would just open the door to more future extortion, wait for them to die off, who knows how long that will take, or to adopt their tactics and start stripping the racists of their rights and privileges, which obviously would just shift the problem rather than solving it.
Also, I feel like people these days are seriously overstating the cultural differences between people to try and carve up the world into these disconnected spheres that can just never understand each other, which is definitely not true. People are largely the same on the inside, they appear to be different because their culture dictates how they express their feelings and, just as importantly, how to interpret the expressions of others. Understanding other people's cultures is largely about figuring out the norms and codes by which they communicate, but once you do, you discover that people everywhere largely share the same hopes and aspirations and that value systems are largely dictated by expediency and self-interest, not by some core cultural impetus.
For example, I don't think that it's somehow embedded in the British DNA to subjugate and exploit other peoples, but they did it because it benefited them and invented whatever rationale they had to justify it. Now that a return to imperialism is no longer feasible and the UK is itself having to push back against the influences of more powerful foreign nations, the British suddenly deem self-determination and sovereignty for all ethnic groups to be at the core of what it means to be British. This doesn't mean that the Brits of the past were bad and those of the present are good, both are simply doing what best serves their interests.