It's not so much that cruise missiles used on civilian targets in South Korea or Japan would not be a reason to start WW3, more that it would be less tempting.
The primary reason that we're concerned about semiconductor fab concentration in Taiwan is that China has consistently stated that it is going to invade Taiwan at some point (and that could be 2049 or in a few years for all we know). This is completely outside of any hypothetical scenarios of who lobs cruise missiles at who during WW3.
You can make the point that relying on semiconductor manufacturing outside of your country/coalition is a bad idea for military self-sufficiency, and I would agree, but that's a much more diffuse risk than the very specific scenario that is driving the CHIPS act and concern about fab concentration in Taiwan.
China has said that they believe that, in the event of hostilities over Taiwan, they will be obligated to strike US forces everywhere in the region -- and the US Navy still has a strong presence in Japan. Also S. Korea and the Philippines.
This means potentially launching missiles at these countries too, and the Chinese have made it very clear to all involved that they will consider and/all US allies in the region as potential belligerents and act accordingly. AKA military action against Japan and SK, and possibly Australia and NZ. It is just another part of the Taiwan political calculus.
Point is: moving the fabs out of Taiwan doesn't mean shit if they're still in a country that China could strike, and in the case of Japan, would likely strike, in the event of hostilities.
Do you have a source for this? I haven't heard this stated before, but I'm not an expert here.
Even taking this as true, I think it's a big leap to go from striking US military bases in Japan, to striking civilian infrastructure in those countries.
It seems quite clear to me that the opening salvo you are hypothesizing (attacking multiple military bases and civilian targets) would be an act of war against the USA and Japan. This would certainly provoke all-out war with the US, and they have a first-use policy that could entail a nuclear response.
Frankly the whole scenario above seems extremely unlikely to me, and I think Ukraine is the better example to model here. Essentially, China occupies Taiwan, and dares the US to strike in retaliation, knowing that their retaliation would be the thing that triggers armageddon, and betting that the US is not actually willing to escalate militarily over Taiwan. I predict that China would take an effort to avoid attacking any US military personnel stationed in Taiwan (I gather this is just an unofficial presence), because the rational play is to give the US as little excuse as possible to escalate in response.
In other words, China MUST offer the US a path to de-escalation/capitulation in order to take Taiwan without a war with the USA. It's much easier to take Taiwan without a full war with the USA (obviously, IMO).
This would be starting World War III. It would be akin to the Japanese attack on Pearl Harbor, with the main difference being, we have thousands of nukes and China does not. This course of action is so profoundly stupid that I cannot imagine China taking it.
China. Japan cooperates with AUKUS [1]. If Xi invades Taiwan, it's going to pull in America, Britain, Australia and–in all likelihood–Japan.
That said, we're more likely to see a recapitulation of the Ukraine playbook than direct intervention by American and Japanese forces.
They want Taiwan not a war with the entire west all at once.
Japan is very able to defend itself against China and the Chinese know that. That doesn't mean the Japanese would win a war with China, but who knows? Who would think Ukraine could take on Russia? If China seriously went to war with the US and Japan China could be blockaded.
The history of the last fifty years suggest the Chinese are pretty measured in their use of force. I'm sure they would try to capture Taiwan if they were confident they could with acceptable losses. But they realize time is on their side and they are not crazy gamblers like Putin.
Japan ? They're as threatened by China as India, and nobody in China is planning for administrative take over of 130 millions Japanese anytime soon. And Japan has so many problems to solve already, they're not looking at bothering China enough to risk missiles.
Countries that have actively threatened Japan with nuclear bombs: China, Russia, North Korea, and the US (which literally dropped a bomb but have yet to make threats since).
It would take a matter of days until they had massive internal protests. Hungry people topple governments in hours.
I think you misunderstand deeply the current equilibrium in the world.
Most of Africa, a significant part of South East Asia, some countries in Eastern Europe would definitely align with China. A significant part of South America would be neutral.
The USA is losing allies nearly as fast as China is making them.
Yet, it is EXACTLY what Xi repeatedly said in his new-term-inauguration speech
The dictator of China has effectively declared, as publicly as possible, and very specifically, that he intends to invade Taiwan if it does not willingly abandon it's democracy and come under China's rule
He obviously thinks he can get away with doing so without consequences, including those you suggest.
Yet, leaders make such mistakes all the time. Putin just made one on 24-Feb-2022.
It is up to the western world to ensure that Xi sees that such an action would result in bad consequences for him, and deter him from his stated course.
But the fact that it is bonkers is no assurance whatsoever that it won't happen.
China can get much further than Russia can in that amount of time.
If chip fabs are at the top list of your worries, your perspective of war is probably overly informed by being on the side that undertakes imperial adventures against people who can't shoot back. Direct war against an actual superpower is horrific.
