You Do Need power plug adapter while traveling from American Samoa to Guinea-Bissau.

Here is Why You Need An Adapter

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

American Samoa

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

Type A

Type B

Type F

Type I

Guinea-Bissau

In Guinea-Bissau, outlets of type C are in use.

Type C