Is there anyone in Australia who has had experience with booking airfares within the United States using the internet?

We can not make bookings from Australia as no airline site will accept a credit card from another country other than UK and Canada. Even the Australian sites we have tried to make the bookings with will not accept the Australian Credit Card.

Can anyone give a site to use that would allow us to book air fares within the US with an Australia Credit Card.

Barbara and James Andrews Salt Ash Australia