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

Here is Why You Need An Adapter

The outlet and plug type used in Northern Ireland is G 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

Northern Ireland

In Northern Ireland, outlets of type G are in use.

Type G