I HATE the way so many USns pronounce Aussie - the "ss" should be pronounced as "zz", not "ss".

Is there a reason the "ss" is pronounced "zz"? And does this mean that Australia is supposed to be pronounced Auztrailia? Does this "zz" sound occur in other Australian pronunciations where an "ss" is present, or does it just happen in the word Aussie? [truly confused-e]