When you are in the Philippines as a citizen you are subject to its laws and regulations, just like anyone else and can also benefit from the free education system there. A US citizen has no limitations as to where he or she can live and no requirement to be in the US. You will always be welcomed back in the US upon your return, with no questions asked. You don't have to "apply" for anything in either country, unless it is for free education in Philippines or food stamps in the US. If and when employed in the Philippines (I don't see why though, since salaries there are much, much less than here) you will have to declare your earnings in Pesos there, but will receive tax credit for any local taxes paid there.
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If you are a United States citizen, then generally it can only be revoked through fraud when obtaining it.
Assuming just one of your parents was a U.S. Citizen, here is the general rule: The parents are married at the time of birth and the U.S. citizen parent had been physically present in the U.S. or its territories for a period of at least five years at some time in his or her life prior to the birth, of which at least two years were after his or her 14th birthday.
If your father meets this test, then there should be no issue, and you do not have to work about your U.S. Citizen expiring. However, if you stay in the Philippines, you would have to meet the test for your kids to be citizens (but this is not the only way for your kids to get U.S. Citizenship).
I agree with my colleagues. Would also point out to make sure you have proof of your citizenship status and that is all taken care of. Even if you are a dual citizen it is important to have proof and carry it with you at all times. Upon entering the U.S. the immigration authorities, Customs and Border Protection, could question you even if a citizen so make sure you have your US passport.
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