In Poland, it's a see-saw - before World War Two, we had only about two-thirds ethnic Poles according to various statistics. Between border movements and resettlement, we ended up with 98% ethnic Poles until 1989, and now IIRC we have one of the largest Vietnamese populations outside Vietnam. It's telling how different various immigrants are treated - Arabs and Asians generally get treated well, blacks tend to get stares and sometimes knee-jerk racist reactions from the football crowd just because they're uncommon, while Romanians, Russians, Belariussians and Ukrainians etc trigger old familiar prejudices at times.

I think the one difference in the Northern Ireland situation is that at sight (and partly even with accent) there's no way to tell if someone's Protestant or Catholic unless they declare their allegiance by words, actions or dress, so it's a bit harder to discriminate against either party. And hey, at least with Poles around you can finally buy decent bread ;)

(Sorry. Was stuck in Ireland for three months on an exchange program in 2004 and got sick and tired of not being able to buy any bread that didn't have the consistency of cotton wool.)