Talk to the publishers of Irish American News or the staff at the Irish American Cultural Center.
It's very commonly used.
I'll point out that you probably never had a conversation with your wife's relatives that began: "So, tell me a little bit about your ethnic background. What are you?"
Oh please - you are talking about an advocacy group that reaches out to those with that common heritage & must define itself as such. - Not with the other 99.99999999999999999999999999999999% of Americans of Irish background.
Please do not presume to tell me what I never started a conversation between my in laws & myself with over a 14 year period. - It makes you look kinda dumb, okay?