You dont understand the point. Its about geographical distance. People dont care about fighting going on halfway across the world. Most Americans/Europeans couldnt give two shits about Australia, and wouldn't if push came to shove.
That wasn't the point I highlighted.
I won;t claim to predict how the world would respond... they may well not. However, I think it would not be in their interests to allow a growing superpower to have unfettered access to Australia and the resources it would allow them. They would not stop with us, and they would know it.
If I were to have a guess, they would allow China to overrun us, but would come to liberate us fairly quickly. If this did't lead to WWIII, then China would start it on their terms, probably with the help of a resurgent Russia.
This is all massive speculation. My point was that our allies would have no difficulty in defending us on our own soil from the Chinese. The difficulty would lie in bringing the war to Beijing.