Looking at my collection of adapters, I see 3 different pin diameters.

The "earthed" (grounded) adapter has a round body and fits down into a matching receptacle (often seen in toilet rooms and other places around water). It has the largest pins (4.8mm ?).

A flat pin to blade adapter has pins which are slightly smaller (4.0mm ?). In the past I've tried to plug it into a grounded receptacle and no power would flow.

A small plugin USB power supply has still smaller diameter pins, which are half metal and half white plastic.

I concur with others who have stated that almost any electronic device you use will be marked 105-240 Volts, meaning you can use it anywhere. The last thing I had that only worked on American voltage was a Palm Pilot.

And, to chime in with others, please please don't stick some metal into the outlet to make it work...that's a recipe for disaster for you, your family, and future room occupants.