We’ve known for decades this would happen. Despite social scientists being overwhelming left-leaning, the conclusions from research pointed to the same outcome. People segregate by ethnicity, among other things, and have less trust for people they see as not being ‘them’. Low trust societies are more dysfunctional, and efforts to somehow make multiculturalism work never lead to something better than what was there before mass-migration.

The best we can say is that integration and assimilation are possible, but numbers must be small enough to prevent new ethnic/cultural blocs from forming. Smaller numbers also reduces threat to the indigenous population, making them more likely to accept newcomers, although there will always be some distance. It’s how people are wired.