On the other hand, when he gets to what he calls the Anglosphere his analysis falls apart. Up to that point his focus is upon tribalism, then all of a sudden he lauds at the Anglosphere's unique ability to absorb and acculturate immigrants.
It feels like Kotkin is saying tribalism rules everywhere except in the English-speaking nations; that is nonsense. I suspect he just knows the Anglosphere better than he knows other realms, so he sees examples of immigrants functioning successfully here.
It isn't clear that the Anglosphere is still doing such a great job of absorbing immigrants. See what you think of his analysis.