American citizens can have their citizenship revoked, but have far less restrictions and more privileges than green card holders.
Unlike green card holders who can lose their permanent residence if they remain outside the U.S. for more than one year without special permission, citizens can travel abroad for as long as they like without having to worry about getting stopped at the gate when they return.
However, naturalized citizens do run the risk of having their citizenship revoked if they leave the U.S. within one year of naturalization to reside permanently in another country.
There are other circumstances that could lead to possible revocation of U.S.citizenship for both born and naturalized citizens. Naturalized citizens will run into problems if it is discovered that they obtained their citizenship and/or green card fraudulently. Examples of this would include a green card secured on the basis of a sham marriage, or the submission of false paperwork that would have been necessary to acquire either permanent residency or citizenship. If the USCIS can successfully prove that citizenship was granted on a false pretense, the guilty party can face revocation of citizenship and deportation. There are other ways that both born and naturalized U.S.citizens can jeopardize their status. They include:
(a) Making a formal, written renunciation of citizenship on a State Department form;
(b) Joining the armed forces of another country and/or bearing arms against the U.S.on behalf of such country;
(c) Engaging in acts of betrayal against the U.S.such as espionage;
(d) If either a born or naturalized citizen acquires citizenship from another country from the age of 18 and up, then U.S.citizenship will be revoked.
This does not include those who have acquired foreign citizenship through parents or grandparents. Even though the U.S.government does not look kindly on the concept of dual citizenship, it accepts the fact that some of its citizens are also automatically looked upon as citizens of another foreign country, based on their family background.