Is it possible for an American Irish to pass as off the boat Irish?
Pretending to be someone you are not will not end good. You need a heck of a lot more than an accent. A job? In Ireland? You can't. Unless you have an aerospace engineering degree or the ability to fluidly translate English language to Gaelic.
No, your American arrogance and overpowering stench will give the game away.
No they'll think you're Mexican.
Not likely. Why be an idiot?
So you want to fake it? You do realise that as soon as you meet an Irish person - someone from Ireland - you'll be outed?