This is not true for most of Western Europe, the notion of an ethnically homogenous population it's an outdated idea of Europe that Americans still hold on to.
In fact, for major parts of Europe it was never true in the first place, the continent has seen centuries of migration of various ethnic groups and cultures before many of today's nation states were even formed.
Pointing to European countries "homogeneity" is just a cheap and borderline racist (they're all white people right, so how can they be ethnically and culturally different?) excuse used by Americans that don't want to examine their own motives.
In fact, for major parts of Europe it was never true in the first place, the continent has seen centuries of migration of various ethnic groups and cultures before many of today's nation states were even formed.
Pointing to European countries "homogeneity" is just a cheap and borderline racist (they're all white people right, so how can they be ethnically and culturally different?) excuse used by Americans that don't want to examine their own motives.