It's true that a bona fide resident of Guam cannot claim ACTC on their federal tax return. However, active duty servicemembers whose military State of Legal Residence (SLR) is not Guam, and who are residing in Guam solely due to military orders, are not considered bona fide residents of Guam.
See pages 24-25 of this reference:
https://www.irs.gov/pub/int_practice_units/JTOPUOP_97_07.pdf
Also, simply using a Guam mailing address on your tax return does not make you a bona fide resident of Guam.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
