One of the many benefits of becoming a U.S. citizen is that one can’t lose citizenship solely by living outside of the United States for a long time.
Making one’s home in another country is a much bigger issue for people who haven’t yet naturalized, but still have a U.S. green card (are "lawful permanent residents"); they can be found to have “abandoned their U.S. residence,” and thus be refused reentry to the United States. For details, see Keeping Your Green Card After You Get It
With a few exceptions, anyone with U.S. citizenship will retain it for life. The exceptions include when one of the following takes place:
- The U.S. immigration authorities revoke the person’s naturalized citizenship. Called “denaturalization,” this will happen only if you obtained your citizenship illegally in the first place, through fraud or concealment of a material fact, or willful misrepresentation. Efforts at denaturalization are rare, though they increased under the Trump administration.
- The person does something that falls under the U.S.’s “loss of nationality” statute. This is found at Section 349 of the Immigration and Nationality Act.) An important thing to notice about this statute is that it contains some wiggle room: The person who performs the relevant act must do so “with the intention of relinquishing United States nationality” in order to lose citizenship. Here’s what the statute lists as acts that might result in loss of U.S. nationality:
- Becoming a naturalized citizen of another country after age 18. If you are a citizen of another country by birth rather than naturalization, this won’t apply to you. (And in any case, there’s that “intention” element of the statute; the very reason that many people can become dual citizens of the U.S. and another country.)
- Joining the military of a foreign state. If you enter or serve in the armed forces of a foreign state and either those armed forces are engaged in hostilities against the U.S. or you serve as an officer (commissioned or non-commissioned), you may be found to have relinquished your U.S. citizenship.
- Joining the government of a foreign state. If you accept, serve in, or perform the duties of any office, post, or employment under the government of a foreign state or one of its political subdivisions (after age 18), and you either acquire that state’s nationality or take a required oath, affirmation, or declaration of allegiance to it, you may be found to have relinquished your U.S. citizenship.
- Performing some act to intentionally give up citizenship. For example, some people file a formal oath of renunciation. They may perhaps because they wish to live in another country, and that country does not permit dual citizenship. (Renunciation has also been in the news lately as some wealthy people have used it as a way to stop paying taxes they owe in the United States.)
- Committing treason or other acts against the U.S. government. Not surprisingly, trying or conspiring to do things like overthrow, bear arms against, or make war on the United States can result in a finding that you have given up your U.S. citizenship.
So, unless something on the above list fits you, the fact that you are living in another country should not affect your status as a U.S. citizen.
If you are still in doubt as to your status, consult an experienced U.S. immigration attorney.