This article examines the changing relationship between Ireland and the United States in the 21st Century and argues that the new security climate within the US following the 9/11 attacks (combined with long-term social changes in both countries) is having a major impact on the relationship between Ireland and the US. The central argument is that Irish-America is undergoing a period of fundamental change, caused by a combination of short-term political factors linked to the attacks of 11 September 2001 and their aftermath, together with longer-term economic and social trends taking place in Ireland which has greatly reduced the flow of migrants from Ireland to the US.