If you were born in Ireland then your grandchildren born in America are Irish citizens if they apply, aren't they?

Anyway, Americans consider themselves Irish/Korean/Iranian/etc down to 2nd or 3rd generation even if the original countries don't. (In fact, all white Americans think they're Irish even if they aren't because it lets them drink in more bars. That's also how America stole all the credit for inventing Halloween.)

The few million people that moved in the 1800-1980 era have a lot more to do with the prevalence of nth generation Irish descendants than people who have moved in the last two decades of property shortages