Many Irish in the northeast (like my great-grandfather) worked in the mines around Pennsylvania and beyond. Montana had a copper mining boom which pulled people across. Butte actually has/had the largest Irish population as a percentage of any city in the US.
Basically someone got offended over something they shouldn’t have and another person asked what would happen if there were quizzes like this about other nationalities.
I don't know about anyone else, but here in the U.S., I have never in my entire life heard anyone say anything negative about Irish people or Catholics. I'm sure there's some old-fashioned bigots out there who still have an axe to grind, but I've never met any.
I remember hearing anti-Catholic comments when Kennedy was running for president. I'm guessing some of the anti-Irish sentiment grew from anti-Catholicism. The KKK was also anti-Catholic and anti-Jew along with anti-African American.
I recall when I was in elementary school seeing Pollack jokes in some old joke books. But... they seemed outdated even then to my 6 year old self. I don't recall ever encountering anti-Irish bias except in historical period films or in what were obvious parodies of outdated racist attitudes. Sometimes you'll see a stand-up comedian joke about the Irish being drunks, or pale, or prone to fighting or something like this, but again, if you understand how these jokes work the primary butt of the joke is not the Irish, but rather the ignorant attitudes of those that the comedian is mimicking. This sort of nuance is very difficult for some SJWs to wrap their head around but it's almost inconceivable that the comics meant it any other way.
I thought everyone and their cat claimed Irish ancestry in America? Where do you draw the line? Being 1/64th decended from someone in Ireland doesn't make you Irish or even Irish-American in my opinion.
As you might guess from my user-name...
I have a T-shirt meme that says "Everyone is a little Irish on St. Paddy's. Except the Danes. We're still Danish."
There are probably more people of Irish origin in California than the entire population of Alaska.