China can take Taiwan today but they don't wanna miscalculate against the US forces spread around Guam, Okinawa, Japan and South Korea even tho they could even yard them off but still they are risk averse and don't wanna miscalculate meaning they are uncertain or wanna wait out until a certain timeline but Taiwan is not coming peacefully as there Airforce is being upgraded as we speak and intend to fight for democracy since they are staunch supporters
China can "Invade" today but as I said unless the Chinese Navy can stop resource and resupply come in from other country, a win is uncertain.
Taiwan is an Island, by that the Chinese Combat Power cannot brought to bear and only limited by the ability of Chinese Navy Sealift Capability, and at this point, It's extremely small, Navy Type 075 is the biggest ship that can land troop in Taiwan, and the Chinese only have 2 of those and they weren't fully operational, and then there are smaller landing dock which can support around 20,000-30,000 troop at any wave, if you put Airborne element on top of that, you probably get around 50,000, Taiwan Western seaboard were defended by at least 200,000 troop and tank. You feed that 50,000 troop in it will just going to get slaughtered...
Also, you can't "Yard" them off like you said because those US Force is in someone else country, you *MAY* have a chance against US Far East Fleet (3rd and 7th) but if you pull Japan, South Korea in, chances are Chinese Navy is going to lose. And you cannot attack US forces in Japan and South Korea without attacking Japan and South Korea
And as long as resource and ammunition and supply keep flow into Taiwan, they will keep fighting, which mean it's by no way certain China will win a war, even without US help. With US help, that's a no contest.
