Some amchair thoughts: Conventional submarines have a battery back up system. They can lie on the ocean floor and be VERY quiet. This is ideal for prowling off-shore of Australia. A nuclear powered submarine has to have cooling pumps operating all the time otherwise the reactor core will overheat. Pumps are noisy! BUT a nuclear powered submarine can go long distances at depth. It does not need to snorkle to recharge the batteries or refuel from conspicious re-supply ships.
Buying expensive nuclear powered submarines from the US is a convenient way of paying "protection" money to have a stable government (i.e one that is not suddenly overthrown by our military in favour of a "more balanced democracy". It is a like the business owner who has to keep paying the local bikie club for "fire insurance". If he stops paying the "fire insurance premiums" he will have a fire. See how valuable the fire insurance policy is!
The ANZUS treaty is a one way promise. Australia blindly supports the US in all its wars of aggression, and in return the US will consider helping Australia if we need help. If you want to see how the US honours its (self appointed) commitments, look at Afghanistan. Australia serves as a intermediate (proxy) target for countries hostile to the US. Rather than attack the US directly, China could take the lower risk option & to show its prowess by attacking Australia. It has said as much.
In a military conflict, Australia is vulnerable to a shortage of fuel. We import refined fuel from places like Malaysia, but this could be easily intercepted, and as a result our nation would have a critical fuel shortage in less than a month. Sure we have "prepaid" the US to store an emergency supply of oil for us, but does any reasonable person think that this will be much help to us in a conflict? If a conventionally powered submarine or any other navy ship cannot get resupplied with diesel, then it becomes a floating pontoon.
China is the new world economic leader, and it has achieved this by commerce not by war. As a nation, we have nothing to gain but a lot to lose by being the "drug-runner" for the US military syndicate.
