Does the USA use a different voltage to Australia?

Yes. Australia uses 240V while the USA uses 110V. Many electrical items are dual voltage these days (i.e. 110/240V) so all you need to do is replace the power plug or use an adaptor. Others are 110V only and so you will need to buy a "step-down" transformer. If you want to buy an item that is 110V only please as step-down transforms from the USA can be shipped with your order and can be significantly cheaper than buying here in Australia.