The New England states have the largest percentage of residents with Irish heritage, according to the U.S. Census Bureau, with New Hampshire at 20% and Massachusetts at just over 19%. It’s no surprise. Boston was the first place in North America to celebrate St. Patrick’s Day—in 1737. Now people with Irish heritage live in every county in the country. With more than 30 million nationwide, the Irish here far outnumber the population of the homeland, with just over 5 million.
Source: https://worldpopulationreview.com/state-rankings/irish-population-by-state