Why do Americans think that Australians live very rough, out in the bush?

I recently got back from Venice and Lake Como, and I met a number of Americans in both places. I don't have anything against America and I am looking forward to visiting the country in Feb 2010, but I thought it was very weird that they were all shocked to learn I wasn't some crocodile Dundee character and that Australia is actually very developed and not some run-down shanty-town. Can Someone explain why they may have thought this?