friendliest people in Europe, why are the Irish so popular etc.
I think Ireland shipped off most of its worst to the US.... the popular American stereotype of the Irish is that of a bunch of morose alcoholics who are quick to resort to violence. The stereotype seems as popular among Americans of Irish descent as anyone else....
For the morose drunk part, see Eugene O'Neill...
For the violent part see popular movie Boondock Saints
There was also the Irish mob, which lasted longer than any other organized crime group except for Italians (the Jewish mob seems curiously forgotten...) the father of one of the title characters in Rizzoli and Isles was an Irish-American mob boss...
Italians are also perplexed by stereotypes of Italian Americans totally obsessed with food.