Transferring Accounts over!!!
Can I transfer my Canadian account to an Australian account and not lose any of my purchases?
Are you currently in the Australia ? You have to be in a country to use its store, that is part of the store's terms, so if you are currently in Australia then that is the only store that you can use.
You can update your country and billing address on your account to be your Australian address. You won't lose any downloaded content, that won't be deleted, but you won't be able to redownload it (that's what your backup is for).
Changing country : Change your iTunes Store country or region - Apple Support