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

Here is Why You Need An Adapter

The outlet and plug type used in Vietnam are A, B and C 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

Vietnam

In Vietnam, outlets of type A, B and C are in use.

Type A

Type B

Type C