I just want to say I agree @Blitzo . A carefully telegraphed intent, warning, escalation, ultimatum can allow China to shoot first without appearing out of blue. It doesnt have to be a surprise attack like Pearl Harbor.
If such a thing were to happen, I suspect the US public/media would still treat it in a manner that portrays it as underhanded, and use it to rally around the flag etc.
And more importantly, the preferred option for the PLA would be if the US was able to signal to the PRC that they will not intervene in a conflict and make material signals to show that sincerity -- i.e.: a PLA strike against US forces in the region is obviously not something to take lightly.
However, if there is ahigh risk of US involvement, and if the PLA carries out a Taiwan operation while US forces and bases in the region are unmolested and allowed to build up forces overall, then that gives initiative to the US as well as offers the ability for the US to concentrate and optimize the redeployment of its forces.