Japan has two separate electicity systems ie 2 different voltages depending on where you are in Japan. I'm not sure but one may be 220v and the other 110v.

As far as things to see:
1) Himeji Castle - the most beautiful building I have seen.
2) Kyoto
3) Nara
4) Hiroshima
If you have time Nikko and Matsumoto were worth a look. Bits of Tokyo are ok as well.

Make sure you get a JR rail pass before you leave the US.

How long do you have there?