Rooney announced his resignation Friday. Obama picked Rooney, the grandson of an Irish immigrant, for the post on St. Patrick's Day 2009.
In an op-ed published Friday in the Pittsburgh Post-Gazette, Rooney said the relationship between the U.S. and Ireland is as strong as it's ever been. He wrote that the countries' common heritage and values creates a "shared kinship" between them.
Rooney supported Obama in the 2008 Democratic primary then campaigned for him during the general election. He was inducted into the Pro Football Hall of Fame in 2000.