Huh. That's a pretty simplistic view, to the point of uselessness.
Voluntary segregation works to a degree, but the nation state model breaks down fast when you consider different groups within. Just look at the problems in Israel with the Ultra Orthodox people, they are hard liners on many issues (women's rights for example).
And what does European mean in the context of the US? Should they just pack up and come home and give the land back to the various native tribes?
Because currently the Nazi problem (white supremacy, racism, fixed gender roles, fixed family structure, fixed sexual orientation - but let's simply focus on the racism thing) is that radical progressives rattle the cage because they see the systemic injustice against natives/others. And reservations (giving [not taking, in this case] land to people) haven't solved shit, they're still hopeless addicts (alcohol/opioids/etc).
In this sense the problem is, that people have too little minds, they lack the big picture. Some people (SJWs) see the injustice and want to go and cuddle the addicts, and blame the people who are better off; whereas other people (alt-right) point at the addicts and have the audacity to sincerely ask "how much money do we want to pour into them?", while of course both groups missing the point that there's a reason why they are worse off.
Accepting that yeah, it'd be good for the natives as a group to "move on" psychologically - even if very strictly speaking it's their right to hold a nihilistic apocalyptic view of the world (after all, their world ended more than a hundred years ago [the last skirmish happened almost exactly 100 years ago in 1918 January]), or accepting that maybe there really was no dog whistling in the H&M jungle monkey hoodie, all of these, of course, doesn't address the current situation of easy to describe groups (like "inner city blacks") having serious problems, and the seemingly paradoxical treatment (give them enough welfare, so they can wither away their lives on cheap drugs).
Indeed, the rationally obvious strategy is to set up a nice and fair triage process and let that decide how much effort/resource should be allocated to solving/treating the problems of various regions, groups, substance abuse patterns, different manifestations of poverty and lack of social mobility. This way it might turn out that solving the problem of Appalachian (mainly white trash) abusing prescription drugs has a higher priority than solving inner city poverty. Or more likely it'll turn out that both need attention, both need resources, both present some high cost-benefit ways to reduce the problems, yet neither are completely solvable withing a generation, nor are either somehow morally more important than the other, but they are both severely worsened by ideologically muddy approach by previous (federal, state and local) administrations and power structures (such as perceived and real admission difference of universities between the aforementioned disadvantaged groups).