Statelessness exists in the United States—a fact that should be of concern to advocates of strict immigration control as well as those who favor a more welcoming policy. The predominant reasons for statelessness include the presence of individuals who are unable to prove their nationality and the failure of their countries of origin to recognize them as citizens. Migrants with unclear nationality, already a problem for the United States, obstruct efforts to control immigration by the deportation of unauthorized aliens. These existing problems of national identity will increase exponentially if birthright citizenship in the United States is amended to exclude the children of undocumented aliens. Contrary to common assumptions, proposed changes to U.S. citizenship law would exacerbate statelessness into the next generation when no fallback nationality is available.