Americans+ Irish accents= 0
Richard Gere is not that bad in this but it still is pretty ropey his effort.
Brad Pitt is *beep* doing it in Devil's Own and Snatch.
Tommy Lee Jones was atrocious in that *beep* film.
Tom Cruise in Far and Away. Ha!
Michael J. Fox in Back To The Future 3. Terrible!
Leave the Irish accents to the Irish or if you want spot-on impersonations a Brit. I;e; Albert Finney,James Mason,Pete Postlethwaite, Daniel Day Lewis, Sean Bean, John Hurt,Robert Carlyle, David Thewlis, Ian Hart, Paul McGann, Iain Glen, Rufus Seweel, etc,etc,etc.