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

Here is Why You Need An Adapter

The outlet and plug type used in Sri Lanka is G 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

Sri Lanka

In Sri Lanka, outlets of type G are in use.

Type G