Why does the U.S. celebrate St. Patty's Day, but not other countrys' "Yay us" holidays?

St. Patty’s is the only big holiday that isn’t religious or focused on the US. Sure, the Irish were among some of our top immigrants, but so were the English – and we don’t celebrate Guy Fawkes Day. Cinco de Mayo is celebrated (at least in my area) mostly by Mexican populations in the US, whereas most Americans will “become Irish for a day” for St. Patty’s Day, regardless of their true heritage. So why is St. Patty’s Day big here?