You Do Need power plug adapter while traveling from United States of America (US) USA to Christmas Island.

Here is Why You Need An Adapter

The outlet and plug type used in Christmas Island is I and in United States of America (US) USA are A and B. This is how they look like.

United States of America (US) USA

In United States of America (US) USA, outlets of type A and B are in use.

Type A

Type B

Christmas Island

In Christmas Island, outlets of type I are in use.

Type I