There's one way to tell different cultures apart that's foolproof: just listen to how strangers greet each other in the street, or how people talk to each other in shops or banks. In America, for example, it's 'Hi, nice to meet you' and 'Have a nice day', normally accompanied by a broad grin.
In Britain there are millions of different rules, depending on the social situation. At a cocktail party, before the beer's kicked in, it might be 'Hello', followed by a pregnant pause, and then both parties saying 'Lovely out, isn't it?' or 'Bit nippy today, don't you think?' followed by each person apologising for interrupting the other, followed by another pregnant pause and nervous laughter, and so on and so forth. Or, if it's two strangers passing in the street in London, it's an almost antisocial silence, where both parties pretend not to notice the other; in the North, it might be an 'Awlrite' or an 'Ello', and a tip of the cloth cap. Whatever it is, if it's your home you understand the rules, so passing people in the street isn't difficult. It's not even an issue.
So why is it so weird in Australia? Well, you've got the good old 'G'day', which is easy and a good way of hiding your nationality under a generic phrase. But just as common – no, more common – is 'How are ya?' phrased as if the person really wants to know. It's not 'Howyadoin'', which is generally regarded as rhetorical: no, the way people say it implies you must answer. But how?
'How are you?' 'G'day' – No, doesn't make sense, but it's something. It's what I use when I panic.
'How are you?' 'I'm very well thank you, how are you' – OK, it's obvious you're a Pom, and it's good for parties, but in the street? You're ten yards past the other person by the time you've said it, and you've left him or her with a question, which is not fair unless you're on the pull.
'How are you?' 'How are you?' – No good, too many questions left unanswered.
'How are you?' 'Good thanks' – This is the one, apparently. When this is the method used, both parts are taken to be relatively meaningless, they're just politeness. If you want to continue the conversation, as you might in a shop or bank where you're there for a couple of minutes, you might append your own 'How are you?' which is a signal for the other person to say 'Good thanks' and then move onto the weather or the cricket scores.
You wouldn't believe how long it took me to work that little piece of social interaction out. And they say that Australia doesn't have a complicated social code...