You Do Need power plug adapter while traveling from São Tomé and Príncipe to United States of America (US) USA.

Here is Why You Need An Adapter

The outlet and plug type used in United States of America (US) USA are A and B and in São Tomé and Príncipe are C and F. This is how they look like.

São Tomé and Príncipe

In São Tomé and Príncipe, outlets of type C and F are in use.

Type C

Type F

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