That isn't really true. There is no concrete threat to Australia for the foreseeable decades, and the US cannot afford to lose influence in the Pacific, so the US will be compelled to act either way much before a threat ever comes to Australia.
When you compare the relationship that Australia has to the US compared to non-EU, non-NATO US allies in Europe and Asia, it's plain to see that Australia is far, far more deferential to the US than it has to be, as nations much more vulnerable and much less valuable tolerate far less.
As expected, nothing in your link details the threat to Australia, it's just about the size of the Chinese military. The problem that no one in mainstream Australian media talks about is that there is not much China can do to Australia now it couldn't before. China's buildup is centered around invading a small island 70km away, and as of today may not be sufficient for that. To go from that to a serious threat to a continent 5000km away has zero credibility.
I think you have serious misunderstanding of what a concrete military threat is. China is 6000km away from Australia by sea, and to get there it has to get rather close to US bases. There is no way that China can do anything beyond standoff strikes to Australia without a crippling cost in the next 20-30+ years. There is absolutely no military threat to the Australian mainland. Conversely, there is very little US submarine bases in Australia do against standoff strikes, so clearly that's not what Australia or the US are worried about (nor should they). In any case any naval power or sustained air power would have to defeat the US first, ally or not, to get to Australia. And if the US can indeed be defeated, then what?
Australia is not meaningfully more threatened by China than, say Brazil. That's just how the geography works out. However, Australia is lot more useful if your goal is to block shipping to and from China, as it is not so far from the straits of Malacca and a good base to contest the island chains (and is, as we've said before, itself very secure).
Unless you think Canada is somehow under a severe Chinese threat, neither is Australia. Australia is far more useful offensively against Chinese shipping, hence why the US will never ever drop it as a basing location unless it really has to.
This, so much. There's so much discussion of "the Chinese threat", but it's just not credible.
The only thing that China would want to invade Australia for is our resources, and they can just buy those. There is at least one mining operation in WA that is Chinese-owned, Chinese-run, entirely staffed by Chinese folks flown in direct from China, and exports the mined resources only to China. They just pay some taxes and royalties to Australia. That is vastly cheaper than any military solution for obtaining the same resources.
I think there's a section of Aussie society that would like China to be a credible threat so that it justifies more military and more fear. But it's just not.
When you compare the relationship that Australia has to the US compared to non-EU, non-NATO US allies in Europe and Asia, it's plain to see that Australia is far, far more deferential to the US than it has to be, as nations much more vulnerable and much less valuable tolerate far less.