Compatibility summary
Your United States plug may fit in El Salvador outlets, as both use at least one common plug type.
Plug comparison
United States plug types: A B
El Salvador plug types: A B
Both countries share at least one plug type (A B and A B), so some plugs may work without an adapter. Check your appliance.
Voltage comparison
United States: 120V, 60Hz
El Salvador: 120V, 60Hz
Voltage difference is within a range many devices tolerate; check your appliance label.