Firstly, i don't think we are a 'part of' Asia.
Australia (due to be renamed once the Flag is changed...because we won't be 'south' of anyone else who are held above our own self worth) is the mainland 'island' you could say, of Oceania and of all the regions of the world, Oceania and Asia are geographically one of the most distant, in terms of relationship.
Its like saying Africa should be 'South Europe or South Middle-East'.
There are those that live by the term 'Australasia' to describe this part of the world, but in truth, this word really belongs to the Indo/Malay part of the world: South Asia.
If all things are equal, just like we try to treat everyone with equality, then the Australasia would make Asia become Borealasia ...but we know Asians prefer to just remain Asia, as they should.
The term Australasia (South Asia) is about as culturally true a description as the word Gaol in the Daily Telegragh ...except that they spell it 'Jail' (get my continental drift
)
As for Bali? Well there are a fair number of Australians who have an interest in Asia and Bali is a close enough taste of it.
Others tend to visit Mauritius, if they can afford it, while others visit Fiji and don't mind if the Military there have more power than Polititians (especially insecure Australian ones who label them as Dictators, because they would rather fight for Greenpeace, than for Political issues.). I myself visit New Zealand as often as I can because their Tourism Industry is the best in the world.
Some say I am wrong.
That Oceania is the region of the world that sweeps from the Silver Fern of New Zealand to the Silverado of Central America/Caribbean. I can see the 'cultural' connection and I always keep this in mind.
Maybe I percieve Australia (PNG) being a part of Oceania in 'difference' to those who see Australia as being part of Asia.
...maybe Australia (PNG) belong to a yet 'unnamed' 8th cultural region of the world somewhere 'near' Asia and Oceania ?
"Oh look everybody! Its the lost continent of Atlantis." Or as Issaac Asimov once wrote of those people that just don't breed as well as everyone else and harbour the act of 'isolationism' (current trend of Australians stating that 'we cannot support a population greater than 35 milion') ..."the Solarians".