It would be a cluserfuck of the highest order.
It would also be telegraphed years in advance just by the sheer number of troops and landing craft needed and they would not have air or naval superiority in any realistic scenario.
Taiwan is heavily defended.
Taiwan can be destroyed (nukes) but cannot be annexed by force in any realistic assessment of capability.
The more I look at it, the more the ancient siege seems more likely than an invasion.
China doesn't want to destroy Taiwan.
Plus, destroying non-Taiwanese vessels and planes trying to break the siege seems like it would be more palatable to Chinese leaders' domestic audience.
China seemed to do a dress rehearsal for this strategy a month or two ago.
Just send a US ship with escort to Taiwan. China would have to attack US military ships to stop it.
I doubt it would happen.
Even fairly primitive mines in relatively smaller numbers (scarcely more than a thousand - China has at least 100,000) in the Iraq War were able to score a mission kill and a major hit on US ships. And that was without US ships actually docking in Iraq.
Do you know how long it took to sweep just over 1000 of those quite primitive mines in Iraq? Around 3 months.
To be clear: I don't like any of these scenarios, but this is my "real politik" view. None of it would be rational for Mainland China, but it is a dictatorship. Dictators don't play by the rules.
I assume you are referring to the United States. Is the US military based in East Asia larger than Japan Self-Defence Forces? Honestly, I'm not sure. JSDF is much larger than most people realize. And to be clear, the UK has almost no presence in East Asia now. Every few years, they have a global tour, but nothing else.
And regarding the Australia submarine deal, France would only build diesel-electric subs. US+UK promised to help Australia build nuclear subs. To me, that is the #1 reason why Australia cancelled the France deal. I am sure they negotiated for months behind the scenes to upgrade to nuclear. When rejected, they announced the Ausuk deal.
The US might not get involved in an all out war over Taiwan but they are likely to support Taiwan in case China attempts a blockade. The US frequently undertakes freedom of navigation drills and would most likely exercise such rights to circumvent China.
Now, will that escalate to a direct conflict is debatable but any genuine threats of nuking US would probably taken as a declaration of war.
1. Chinese naval blockade of Taiwan
2. US will send navy + air force from Japan bases.
3. No shots fired between US and China (too risky due to both nuclear powers).
4. Optional: China may immediately claim sovereignty over Taiwan without negotiations with Taiwanese gov't.
5. China will declare that any attack on Chinese military (in the area) or military aid to Taiwan will be viewed as an "invasion" (whatever that term really means). Thus, China will declare that the use of nuclear weapons is valid to protect against invasion by US military.
6. This declaration will be interpreted by US as a nuclear threat.
7. China will refute this US claim.
8. Conclusion: US-China stalement with words only. China takes Taiwan.
To refine my earlier post, simply threatening to (nuclear) bomb / torpedo a US navy carrier strike group is enough. No need to threaten US territory. I'm not sure ICMBs from mainland China can reach mainland US, but they can certainly hit Hawai'i and other US posessions. Also, they have nuclear warheads on subs. I doubt they will work on first try, but the threat is great enough to force US to standdown.Lastly, I don't like or support any of this, but, it is the most likely scenario.