One of the reasons we had planned to defend Taiwan ROC is that we were counterbalancing the spread of communism. Global communism has essentially collapsed and those communistic countries remaining have a lot of capitalism in them now. I'm less concerned with the communism aspect of China PRC and more worried about the growing capitalism. With an increasing economy the PRC is becoming a rival to the US. China's imports of petroleum and other resources is going to strain global resources and raise prices for US consumers. This will lead to war. Taiwan is simply a lever to be used to instigate hostilities when China (or the US) feels ready. The PRC know this as does the US, NATO, Russia, and just about everybody, even though they may not publically admit it. North Korea is another potential trigger. In fact, I suspect NK will create a diversion allowing for a real or feigned attack on Taiwan ROC to force a move by the US.
True to Sun Tzu the PRC is trying to wedge our alliances, like ANZUS, apart. But to our credit we've got Pakistan nominally on our side when the PRC would prefer it was their counterbalance to India which is a thorn in their side. Russia seems to be on their side as they sell weapons to the PRC, but Russia sells weapons to anyone... and Russia has always been ill at ease with the overpopulated PRC next to their underpopulated and resource rich siberian territory.
In the Line of Fire are Taiwan ROC, Japan, and South Korea which have adequate defenses but would probably need to be buttressed by the US in the event of a concerted attack. The potential enemies of our potential enemy are Russia and India. India might be countered by Pakistan and Russia's ability to mount a viable defence along China's border is iffy. So how do three countries defend against or defeat a massive land army if they can't get enough men and equipment into the theater of operations? [Jack Ryan voice]How do you get three nuclear powers to stop China...[/Jack Ryan voice]
So China's posturing and saber-rattling is probably nothing more than a dry run for a prelude to global thermonuclear war.
Have a nice day.