The hypothetical war in Taiwan would likely be almost entirely naval/aerial so yeah the question is if US has enough political will. Don’t think artillery shells will be a huge factor and even on paper the Chinese navy (and probably the air force) doesn’t even come even remotely close to US (yet).
Actual invasions of Japan and Australia are even harder to imagine. How would that even work? And why?
Artillery and particularly guided artillery like Excaliber rounds are highly effective at resisting landings.
In the most recent US wargame, China succeeded in occupying parts of Taiwan which would make artillery even more important — as attacks from the mountain regions towards Chinese occupation would keep them from establishing a secure foothold.
War games can be very deceptive though. Back in 2019/20, 2 separate studies ( Polish and US) expected that it would only take Russia 4-5 days to get to Warsaw with Polish units sent to the border suffering 60-80% casualties.
To be fair NATO wasn’t taking really taking defense that seriously back and maybe they had a point, although considering what happened in Ukraine that seem like a very unlikely outcome (unless Britain/France/Germany decided to stay out and not risk their air forces ..)
I guess overestimating your opponents is usually better than the opposite. OTH had Britain/France not made that mistake in the 30s much of WW2 could have been prevented.
The purpose of wargames is to find holes in your defense and the shore them up. If your war game doesn't find holes you are probably doing it wrong. In the real world your enemy doesn't have spies everywhere, but in a war game you should give them spies everywhere just because you won't know where those spies are and so everything could be compromised.
China-Taiwan situations is technically still a civil war. Internal conflict to "China". Like war between Confederacy and Federation forces.
It is unlikely that China will invade Japan and certainly not Australia. I find it extremely more likely that USA will invade Mexico with some fake pretence like war on drugs.
Actual invasions of Japan and Australia are even harder to imagine. How would that even work? And why?