Australians definitely have a reputation among Americans for being friendly (if bad tippers). Until recently I was pretty sure it was true, and I'm not convinced it's not, but I've been wondering if perhaps Americans have been mistaking some of Australians' "congenial" mocking as congenial, when in fact, sometimes, it's outright mocking. We expect it of the British (at least those of us who've stopped to think about it), but I have a theory that a significant percentage of Australian mocking goes over American heads in what they perceive as genuine friendly banter.
Then again ... wait. I was going to say we do that, too, but, actually, I think it's just me. Sorry everybody.