This working paper addresses the challenges posed by Huntington (2004) regarding the impact of immigration on American identity. The authors contend that Huntington is correct in arguing that the American identity is in fact eroding. However immigration is not the mechanism through which this erosion has occurred. Instead the authors argue that it is due to the attrition of constitutional rules. Initially these rules were designed to provide a relatively higher payoff to activities supporting the American Creed. This has since changed so that the payoff to activities running counter to the Creed have increased. The main conclusion is that while historical traditions and cultural factors play a role in political and economic development, they should not be overestimated. While immigrants come from a diverse set of backgrounds, the American Creed can in fact be learned. Policy should not focus on restricting immigration, but rather on creating binding rules that prevent the erosion of the American Creed and identity. Keywords: American Creed, assimilation, culture, immigration, national identity.