What do you think caused the World Wars? Or, to give a more recent example, consider the discrimination East Europeans faced after their countries joined the E

What do you think caused the World Wars? Or, to give a more recent example, consider the discrimination East Europeans faced after their countries joined the EU and many of them immigrated to the West. Europe is not the US. People from other European countries (and from many traditional minorities in the same country) are obviously different as soon as they start speaking. Many Europeans live outside their home country and most visit other European countries once in a while. There is a huge number of encounters between Europeans from various cultural backgrounds every day, and sometimes your background marks you as a member of an outgroup. And nobody is really excluded from that.