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).