Irish Americans are generally held with disdain among Irish people, because they're so far from being Irish but insist upon it so much. So many of them talk about their Irish heritage if they have one Irish ancestor, even though they usually have more english or German ancestors than Irish. It's just white Americans with no sense of identity finding one thing in their heritage and deciding to make that their identity, without having any knowledge of what Ireland is actually like. The most obnoxious ones will come to Irish people expecting applause for having Irish ancestors, but they won't know extremely basic stuff like what currency Ireland uses or that "Patty's Day" is not what Irish people call St Patrick's Day.