Originally Posted by alanR
Tsk, tsk, especially considering the oath people take to become US citizens requires them to give up such loyalties and even more amazingly requires them to give an oath to God.
I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty of whom or which I have heretofore been a subject or citizen; that I will support and defend the Constitution and laws of the United States of America against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I will bear arms on behalf of the United States when required by law; that I will perform noncombatant service in the Armed Forces of the United States when required by the law; that I will perform work of national importance under civilian direction when required by the law; and that I take this obligation freely without any mental reservation or purpose of evasion; so help me God. In acknowledgement whereof I have hereunto affixed my signature.
But this only when one applies for US citizenship when one would otherwise have no right to it. People who have right to dual citizenship are generally permitted to hold dual nationality (myself included). There has been a Supreme Court case or two in which the Court ruled in favor of people to remain dual citizens who had that right from birth (even if they were not passport holders their entire life) when US authorities attempted to strip them of the US citizenship.
Losing US nationality is pretty difficult and generally requires (from what I have read), one does some pretty bad things to upset the US government (i.e. serving in the armed forced of another country, although I believe Israel is an exception to that rule).