Getting hammered on St. Patrick's Day is a longstanding tradition - in America. St. Patrick's Day wasn't a big party in Ireland until AFTER Irish Americans started doing it. Here are some other traditions that aren't actually Irish.....
1. Pinching people for not wearing green. America invented it and not many enjoy it.
2. Drinking green beer. That's another one we came up with. Most bars in Ireland don't serve it. If you want to be authentic, drink Guinness or Irish whiskey.
3. Drinking Irish Car Bombs. That's when you drop a shot of Irish whiskey and Bailey's into a pint of Guinness, and chug it. A guy in Connecticut came up with it in 1979.
But the name is a reference to the terrorist attacks in Ireland when the IRA was active, so obviously a lot of Irish people think it's offensive.
4. Wearing green leprechaun top hats. In traditional Irish folklore, leprechauns wore pointy hats - and they were RED. Not to mention that St. Patrick was traditionally associated with the color blue.