Citizenship of the United States
A person who is considered a citizen by more than one nation has "dual citizenship". It is possible for a United States citizen to have dual citizenship; this can be achieved in various ways, such as by birth in the United States to a parent who is a citizen of a foreign country (or in certain circumstances the foreign nationality may be transmitted even by a grandparent) by birth in another country to a parent(s) who is/are a United States citizen/s, or by having parents who are citizens of different countries. Anyone who becomes a naturalized U.S. citizen is required to renounce any prior "allegiance" to other countries during the naturalization ceremony; however, this renunciation of allegiance renunciation of citizenship to those countries.
Citizenship
The United States has a federal system in which a person is a citizen of their specific state of residence, such as New Jersey or California, as well as a citizen of the United States. State constitutions may grant certain rights above and beyond what are granted under the United States Constitution and may impose their own obligations including the sovereign right of taxation and military service; each state maintains at least one military force subject to national militia transfer service, the state's national guard, and some states maintain a second military force not subject to nationalization.