Actually, the fact that they are an independent country does not mean they can’t be granted statehood in the USA: Vermont and Texas were both independent countries until the point when the joined the Union.
Independent countries can be granted statehood by treaty and act of Congress as happened in those cases.
Of course, I see no evidence the Philippines wish to become the 51st state, and I’m not sure how prudent it would be since we would pick up the MILF and Abu Sayyaf insurgencies.
The time for this is long past. Interestingly when the Philippines were under U.S. control after the Spanish-American War, there was a Muslim uprising which General Blackjack Pershing put down (with tactics which included exploiting the Muslim horror of pork). After the rebellion was suppressed the Muslims in the Philippines were among the loudest advocates of pursuing statehood, since they decided that the First Amendment would give them a better deal then being in an independent majority Christian country without an explicit guarantee of religious freedom.
Puerto Rico also doesn't want to become a state, they have voted it down several times in the recent past.