That said, as good as your point is about African American culture, it's far from our youngest; there's also the Chinese and Italian migration waves, the Armenian refugee wave... On the west coast, you would definitely also have to consider the effects of Japanese internment during WWII. That might be the most recent, but I wouldn't be surprised if there was another wave between now and then.
This doesn't detract from your overall point, or the severity of the effect on specifically African American culture, but I don't think you can call that America's youngest culture.
Further, there's evidence being brought out that there actually were aboriginal Americans that we would call black.
A simple example is being good at multiplication in kindergarten. This small advantage can become a desire for continuous academic excellence via courage towards math. If a child's parents are stereotypically prudish, another "advantage" is the ability to sidestep distractions of athletics/sex.
If the natural momentum a culture can build isn't appreciated, people become shallow and hoarding. In my family for example, the idea that Asians are naturally smarter and Blacks dumber is common and was the impetus for my thoughts in this area. I see a greed and lack of empathy developing that is difficult to watch.
The most common actual real world usage I get out of explaining this model is more support for affirmative action. Perhaps other people can see it as having other value. No need to trash it. All models are simplifications of reality and thus "wrong".
The Asian cultures have centuries more experience dealing with high density people situations. Violence is not as legitimized as a method of boundary enforcement for example because people have learned to deal with each other without killing each other. Sure it creates super thick-skinned rudeness (China/NYC/India) or super thin-skinned rule following (Japan) but boundary enforcement based on things like status markers(Like LV bags and iPhones) or rules or much better than those based on violence.
The U.S. is unique in its sheer mix of cultures but also because of the presence of its youngest culture (African American culture) that is today still reeling from the shock of being torn from its mother culture in Africa. Racism and the lack of a reliable justice system for them has forced their culture to rebuild from 0, going through stages where each person had to have the ability to dole out personal-justice/violence.
What's normal in China becomes rude in the U.S. What's justice in one culture is violence in another.
The locals who call a place home see this and want to preserve their own culture. Despite economic incentive allowing them to move anywhere else, their dollar is limited by their software in what it can do. It's like a project that has github dependencies forced to only use dependencies on some other place like gitlab. The project might as well die and start over. And though projects and start over, people can only die, and they will go down swinging.
Younger and newer cultures learn to be more flexible and adaptable. The software/culture limitation that prevented their parents from living like kings in Thailand is removed because their dependencies aren't as rooted. Some are even completely standalone and super flexible at the cost of having no way of influencing things. (eternal vagabonds w/ no long relationships)
Meanwhile new dense hardware developments can only be populated by software that can deal with the density and find it worthwhile. Thus you get H1B 'slave houses' filled with Indians/Chinese.