You Do Need power plug adapter while traveling from Portugal to American Samoa.

Here is Why You Need An Adapter

The outlet and plug type used in American Samoa are A, B, F and I and in Portugal are C and F. This is how they look like.

Portugal

In Portugal, outlets of type C and F are in use.

Type C

Type F

American Samoa

In American Samoa, outlets of type A, B, F and I are in use.

Type A

Type B

Type F

Type I