Question

What is double citizenship? Why does a person living in USA has a citizenship of America as well as of United States ??

Answer 1

It means that as far as the United States is concerned, you are a citizen of the United States and have the same rights, privileges, and responsibilities as any other citizen, but that another country also recognizes you as a citizen of that nation. The U.S. State Department does not track the number of people who hold U.S. and other citizenships. As this State Department Web site points out, while the United States does not prevent dual citizenship, it does not encourage it either because of the potential for conflict in being subject to the laws of more than one nation. For dual citizens the country of residence is generally considered to have the greater claim on allegiance. 

The most common routes to dual (or triple or more) citizenship are birth, marriage, or naturalization. For example, if you are born in the United States, you automatically become a citizen here. But if your parents are nationals--citizens--of Mexico, for example, you will also be a Mexican citizen. If your parents are each citizens of different countries, neither of which is the United States, and you are born here, you could have triple citizenship at birth, depending on the laws of your parents' countries. Conversely, if both your parents are Americans who are living abroad when you are born, you will again be considered an American citizen and possibly a citizen of the nation of birth, depending on what their rules are. The laws regarding dual citizenship by birth can get quite filigreed, depending on whether both parents are Americans, if they are married, and which parent is the foreign national.

Some nations confer citizenship if you marry a national of that country. For example, if an American marries a Greek, the American also gets a Greek citizenship. Marriage to an American by a foreign national does not convey citizenship here, just an expedited shot at it. People who become naturalizedAmericans--that is, they were born citizens of another country but through a legal process become Americans--do not have to give up citizenship of their previous country. In some cases they can't because some nations do not allow people to give up their citizenship, even if they become naturalized citizens of the United States. But the United States expects such naturalized citizens to have primary allegiance to the United States. Dual citizens can, if they want to acknowledge the duality, be issued passports for each country of which they are citizens. But someone with a dual U.S. and other citizenship who gets in trouble abroad, particularly in the country the person holds the additional citizenship in, may not be able to get the same assistance from the U.S. embassy there as an American who has no additional citizenship.

Another potential source of trouble for a dual citizen is getting one's American citizenship revoked. For example, serving as an officer in a foreign military, or having a high-ranking position in a foreign government has the potential to endanger U.S. citizenship. But the ruling principle is that by undertaking these actions one intends to give up American citizenship. It is also possible to voluntarily renounce U.S. citizenship, but simply wanting to stop being an American is not necessarily enough to make it happen. Ask Marc Rich, the fugitive financier who has multiple other citizenships but has not been able to get rid of his U.S one. To start the renunciation procedure, you have to be outside of the United States and swear your oath of renunciation to a U.S. consular officer. If the State Department in Washington grants the request, you are given a certificate of loss of nationality. That decision is irrevocable. That is, you can try to become a U.S. citizen again, but you have no special advantages toward that goal over other foreign nationals.