All visitors from USA or citizens from countries under the US visa waiver program get 30 days on arrival.
You may be required to show you have an onward ticket and enough money to cover your stay.
American Samoa is under US control, all consular matters should be directed to a US embassy.
For a visa you need to contact the Attorney Generals office on +1 684 633 4163
To apply email firstname.lastname@example.org