Guam is considered a U.S. Territory, not one of the U.S. 50 states. When entering your address in personal information, state drop down menu has foreign/us possession as an option if you are still living in Guam. However, that information only relates to the fact that you can file using an unusual address for correspondence reasons.
You should be able to file your federal and state returns as usual, just declaring your US wages.
As a US citizen or resident alien, you need to report your worldwide income no matter where it is received or earned.
