You need an ETA for American Samoa if you have a Japanese passport

Travelers need a travel authorization to visit American Samoa for Business or Tourism. Visa-exempt visitors entering American Samoa must obtain an Electronic Travel Authorization (eTA). Travelers can submit the eTA application online. Once the application is approved, travelers receive their eTA confirmation electronically. An eTA is electronically linked to a passport. If travelers receive a new passport, they must apply for a new eTA. A valid eTA is required to board the flight. If the eTA is expired or doesn’t match the traveler’s passport information, travelers will not be able to board their flight.