You Do Need power plug adapter while traveling from Great Britain 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 Great Britain is G. This is how they look like.

Great Britain

In Great Britain, outlets of type G are in use.

Type G

American Samoa

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

Type A

Type B

Type F

Type I