You Do Need power plug adapter while traveling from South Korea 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 South Korea is F. This is how they look like.

South Korea

In South Korea, outlets of type F are in use.

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