Easter Island (airport code "IPC") is considered part of South America for Oneworld Explorer purposes. Not sure about the Global Explorer, but I know from first hand experience that one can do a round trip to IPC on an Oneworld Explorer.
If you want to see a trip report I did on my Easter Island experience, do a search in Trip Reports under my name.
It is a great experience and one I would highly reccomend. Not a bad way to earn miles either!