Australia's biggest risk of collapse is from major disruption to its supplies of petrol and diesel.
Australia has virtually no oil refining capacity left (despite being a substantail oil producer) and imports almost all its petrol and diesel from overseas, mainly Singapore. Refined products enter Australia at just a handful of ports.
If these supplies were disrupted, by war, terrorism or natural disaster, Australian cities would quickly collapse.
With no fuel for trucks (or the limited rail capacity) the country would grind to a halt and food supplies would quickly evaporate in cities, which are very far from the farms.
Yeah, I don't disagree at all. Australia keeps running almost exclusively on trucking transportation. I didn't realise the lack of oil refining capacity... I can see how it would be an easy function to offshore, but it's obviously not very resilient.
As oil gets more expensive to extract (ie, drills have to go deeper, etc) and both shipping and trucking transportation gets more expensive as a result, Australia is definitely going to feel the pain of that lack of oil refining capabilities.