美国承认双重国籍。双重国籍，是指一个人拥有两个国家的合法公民身份，也就是拥有两个国家的国籍。即一个人通过一个国家的法律获得该国国籍，又在另一个国家再一次通过该国的法律获得该国国籍，就被视为拥有双重国籍。
美国认为，在美国领海内的商船上出生的人取得美国国籍。如果一艘英国商船停泊在美国港口，则在该船上出生的人即同时具有英美两国国籍。如果新生儿的父母不是英国或美国公民，其国籍国采血统主义，则他还同时具有父母的共同国籍，如果其父母的国籍不一致，则还可能出现四重国籍。
扩展资料
中国政府处理双重国籍的态度是：
1、坚持一人一国籍，不允许任何中国公民有双重国籍。
2、尊重本人意愿，不强制或违背本人意愿选择国籍。
3、如果中国公民在他国获得他国国籍，则视为自动放弃中国国籍。但有必要时可以恢复中国国籍。
中国的《国籍法》中明令规定不允许任何中国公民有双重国籍，如果获得他国国籍，则视为自动放弃中国国籍。
参考资料来源：百度百科——双重国籍
新移民在加入澳大利亚国籍后保留原有之国籍，但不可以再加入澳大利亚国籍后再申请加入其他国籍，否则你就必须放弃澳大利亚国籍。
澳洲政府已经废除1948年澳大利亚公民法第17章，从2018年起，就无限制的允许双重国籍了。
美国法律并没有强制规定一个拥有双重国籍的人士在两个国籍中选择一个国籍。同时，若是一个人在“自动”的情况下取得他国国籍的人士也不会影响到其美国公民权。但是，若是一个人“自愿”的“选择”申请其他国籍的身份，而有意于放弃美国公民身份时，就会丧失其美国公民的身份。
扩展资料：
承认双国籍的部分国家
澳大利亚、比利时、加拿大、克罗地亚、塞浦路斯、捷克、丹麦、埃及、芬兰、法国、德国、希腊、匈牙利、冰岛、爱尔兰、以色列、意大利、卢森堡、马耳他、墨西哥、新西兰、巴基斯坦、菲律宾、葡萄牙、罗马尼亚、南非、韩国、西班牙、瑞典、瑞士、土耳其、英国、美国等。
不承认双国籍的部分国家
奥地利、中国、印度、印尼、日本、哈萨克斯坦、马来西亚、爱沙尼亚、立陶宛、荷兰、尼泊尔、挪威、波兰、新加坡、泰国、乌克兰、阿联酋、坦桑尼亚、委内瑞拉等。
参考资料：百度百科-双重国籍
参考资料：人民网-澳最高法公布双重国籍争议裁决
具体来说美国公民（citizen）和美国国民（national）是有区别的。公民肯定是国民，但是反之则不一定。特殊情况是出生于美属萨摩亚和斯文群岛但父母不是美国公民的人。
双重国籍通常的情况是指美国父母在海外出生的子女根据属地法取得当地国籍（比如德国）或外国人在美国归化成为美国公民当不放弃原国籍的情况。美国不鼓励双重国籍，特别指出具有双重国籍的美国公民在一些情况下不能得到美国的领事保护。比如你有美国德国双重国籍，但在德国被抓起来关监狱了，美国使领馆没法提供任何保护。如果美国公民在其他国家归化入籍，除非正式声明放弃美国国籍（并交税），不认为是自动放弃美国国籍。
Dual Nationality
Section 101(a)(22) of the Immigration and Nationality Act (INA) states that “the term ‘national of the United States’ means (A) a citizen of the United States, or (B) a person who, though not a citizen of the United States, owes permanent allegiance to the United States.” Therefore, U.S. citizens are also U.S. nationals. Non-citizen nationality status refers only individuals who were born either in American Samoa or on Swains Island to parents who are not citizens of the United States. The concept of dual nationality means that a person is a national of two countries at the same time. Each country has its own nationality laws based on its own policy. Persons may have dual nationality by automatic operation of different laws rather than by choice. For example, a child born in a foreign country to U.S. national parents may be both a U.S. national and a national of the country of birth. Or, an individual having one nationality at birth may naturalize at a later date in another country and become a dual national.
U.S. law does not mention dual nationality or require a person to choose one nationality or another. A U.S. citizen may naturalize in a foreign state without any risk to his or her U.S. citizenship. However, persons who acquire a foreign nationality after age 18 by applying for it may relinquish their U.S. nationality if they wish to do so. In order to relinquish U.S. nationality by virtue of naturalization as a citizen of a foreign state, the law requires that the person must apply for the foreign nationality voluntarily and with the intention to relinquish U.S. nationality. Intent may be shown by the person’s statements and conduct.
Dual nationals owe allegiance to both the United States and the foreign country. They are required to obey the laws of both countries, and either country has the right to enforce its laws. It is important to note the problems attendant to dual nationality. Claims of other countries upon U.S. dual-nationals often place them in situations where their obligations to one country are in conflict with the laws of the other. In addition, their dual nationality may hamper efforts of the U.S. Government to provide consular protection to them when they are abroad, especially when they are in the country of their second nationality.
U.S. nationals, including dual nationals, must use a U.S. passport to enter and leave the United States. Dual nationals may also be required by the foreign country to use its passport to enter and leave that country. Use of the foreign passport to travel to or from a country other than the United States is not inconsistent with U.S. law.本回答被网友采纳
但澳洲政府将废除1948年澳大利亚公民法第17章，从明年起，就无限制的允许双重国籍了
美国法律并没有强制规定一个拥有双重国籍的人士在两个国籍中选择一个国籍。同时，若是一个人在“自动”的情况下取得他国国籍的人士也不会影响到其美国公民权。但是，若是一个人“自愿”的“选择”申请其他国籍的身份，而有意于放弃美国公民身份时，就会丧失其美国公民的身份。