I'm not especially "intune with Europe", and that conflict ended when I was a small child, but I knew the violence extended to civilians. Not sure why you assume people wouldn't know that.
I'm referring to the average American populace and not to the average HN poster. For example, I knew the details of the Tokyo Sarin Gas attacks and know that it was caused by a "new religion" cult but an average person outside Japan wouldn't really remember that as clearly as I am (unless you are somehow in Western Australia since a farm area there was refurbished to produce sarin). It is like 9/11 outside America: an average person knows it enough to remember whatever inconvenience they encountered that day but not the whole details.
Sunday Bloody Sunday is a well known song, don't forget. It wasn't that long ago that the IRA was putting bombs in trash cans. I think this is far more known in the US than you'd think, especially given it's intra-Christian violence.