An interesting point is made in the NY Times recurring talking head series "Room for Debate" by one Hastings Wyman, in this case, on why the South is more right-wing than the rest of the USA. Well, actually he could have made it slightly better, so I'll make the slightly better version:
There were two ethnic groups alone in the South, and pretty much nobody else, unlike pretty much the rest of the country. The native Americans were largely exterminated or ethnically cleansed.
So there weren't really Irish to realize that in their being picked on by the WASPs, they were in solidarity with Germans, Jews, Poles, Italians, and, yes, African Americans and Latinos.
I think it's one of the cases where if we can see our common state of dukkha, we're a bit better off; a smidgen of suffering is transcended right there.