TIME TO CANCELL $400 BILLION AUKUS SUBS !!!, page-124

"alliance are only as good as the willingness of the allied countries to come to each others' aid in the event that defence is required against an aggressor."

I think you've started that thought a step too far in. The first purpose of an alliance is to act as a deterrent against a potential aggressor. IMO the point, really, is to deter any attack to begin with because the attacker see that it's likely going to be too costly for them to achieve anything. Insurance policy.

IMO the US basing B52's & subs here, marines in Darwin, together with AUKUS, Pine Gap, 5 Eyes, ensures that deterrence. Like you alluded to, just being 'good mates' mightn't be enough in the future if USA turns more isolationist.

Re what the Chinese might do in the future, yes extreme naked aggression is unlikely, but who knows. They've shown in the SCS that once they get the capability they are prepared to violate claimed territory of other countries. What I do think is it's much less likely we receive any physical coercion while allied to the US - Just like it's much less likely the Baltics will be hearing from Russia due to article 5, than if they were on their own.

Cheers!