The entry requirements for Guam are largely the same as those for the US, and nationals of all countries not needing a visa to enter the U.S. do not need a visa to enter Guam, although they may require an ESTA travel authorization. Foreign citizens may enter Guam using one of three options: (1)- the U.S. Visa Waiver Program, (2)- the Guam/CNMI Visa Waiver Program or (3)- a valid U.S. visa. If you are using the Guam/CNMI Visa Waiver Program, you do not need to apply for a travel authorization prior to going. The Guam/CNMI Visa Waiver Program includes seven U.S.-VWP countries (Australia, Brunei, Japan, New Zealand, South Korea, Singapore and the UK) plus Hong Kong, Malaysia, Nauru, Papua New Guinea, Taiwan and Russia (from 15.01.2012). Foreign citizens using the U.S.-VWP may stay 90 days, while citizens using the Guam/CNMI-VWP may stay for 45 days. Citizens of non-VWP countries must apply for a U.S. visa at any U.S. embassy.
All visitors to American Samoa require a passport valid for six months or more, a return ticket or onward ticket and enough funds to support your stay.
US Citizens and US Nationals do not require a visa and may enter and leave freely.
Canadian, Australian, New Zealand and United Kingdom citizens may enter Guam and will be issued with a 30 day entry permit.
All other international passport holders intending to visit American Samoa for business or holiday are required to apply for an entry visa. The rules are the same as USA.