While recognizing the existence of dual nationality, the U.S. Government does not encourage it as a matter of policy because of the problems it may cause. Dual nationality may hamper efforts by the U.S. Government to provide diplomatic and consular protection to individuals overseas. When a U.S. citizen is in the other country of their dual nationality, that country has a predominant claim on the person. A foreign country might claim you as a citizen of that country if (a) you were born there; (b) your parent or parents (and sometimes grandparents) are or were citizens of that country or (c) you are a naturalized U.S. citizen but are still considered a citizen under that country’s laws. (The oath you take when you are naturalized as a U.S. citizen (8 CFR 337.1) doesn’t mean the foreign country does not still regard you as a citizen of that country.) Public inquiries about the citizenship laws of other countries should be directed to the embassy or consulate of that country in the United States. 8 U.S.C. 1185(b) (Section 215(b) INA) and 22 CFR 53.1 require that U.S. citizens exit and enter the United States on a U.S. passport, with certain limited exceptions (22 CFR 53.2).
Under Singaporean law, an individual who automatically acquires Singaporean citizenship at birth retains that status even after acquiring U.S. citizenship. Singapore does not recognize dual nationality beyond the age of 21.
If you wish to renounce your U.S. citizenship, please send an email with your full name, date, place of birth, U.S. passport number and residency status in Singapore to firstname.lastname@example.org