Booking American Flights Online

Booking American Flights Online

I've been having a 'slight' problem with booking flight tickets online within the U.S. It turns out that all major online booking sites only accept registration from people who live in the U.S. And the very few Australian ones have prices that are double the American ones. And I really don't feel like paying an extra $700.

Not exactly sure what to do about this. Does anyone know of sites which allow to book online from Australia for flights within America and don't cost twice as much?