I'm an American living in Okinawa Japan, Just bought an apple os-x now I'm trying to buy some movies, but not authorized because my computer is American is there a way o get around this?

It's a billing issue > The Complete Guide to Using the iTunes Store | iLounge Article

Same policy for iTunes as well as the Mac App Store.

It isn't that your Mac is US, it's that your bank is US. To buy from the store for a country, you must be a resident and have a bank card from a bank in that country with a billing address in that country.

If you have a US bank card with a US billing address, you should be able to buy from the US store, even from Japan.