There was this congratulation phone call between Taiwan and the then President-elect Trump back in 2016.
There were people that attributed that as a blunder by Trump as novice in foreign policy.
The 1979 deal with China to replace US diplomatic relations of Taiwan with Beijing followed by ending in 1980 the US-Taiwan Defensive Pact, amidst the Vietnam ping pong smoke, and was according to many done to isolate the Soviet-Union from China. Russia the Cold War opponent with a big nuclear and China at that moment only a giant without military and economical teeth. A rural agricultural economy that had yet to start with its 1 child per family policy, but already a mighty partner potential for the Soviet-Union.
With the growing strenght of China minor steps were taken by US Presidencies to keep Taiwan in good economical order, but nothing that really did upset China and the world order.
China however did change the world order, by getting economical teeth, by its focussed trade economy and the Soviet union is replaced by a much smaller Russia that is economically only growing slowly.
I think the geopolitical move that Trump has in mind, since before his election, is to redirect the bulk of the geopolitical US attention from Russia to China.
Some sanctions on Russia, redirecting the EU towards Russia and vice versa, some actions towards the EU, should contain Russia and the EU. The Middle East the usual mess with various kinds of opportunities if needed.
China the main dish.
My guess has always been that Trump has a simple agenda he sticks to. What he said about that caused many Republican representitives to be critical.
He made also already during the elections and at the beginning of his presidency the promise that Republicans that would not follow him would face the wrath of his Trump voters base.
In the past 17 months he has meanwhile a team around him that is good enough in yes-nodding and most of the Republicans representatives are quieted.
Meaning that the traditional anti-Russia politics is somewhat contained and the anti-China politics has more room to pick up his simple agenda point on China that started with that Taiwan phone call in 2016.
Does a naval base in Taiwan fits that strategy ?
IDK about military vulnerability and implications. But it feels anyway as a bit drastic.
China promised already war on Taiwan (not on the US) , if the US would make further smaller moves with Taiwan. But to have military teeth China needs a lot more spending at defense than now, weakening economic growth to keep its people happy, especially if that is combined with US trade issues.
Will the Taiwanese people be comfortable with that war threat, or rather prefer to join China in 2 generations or so when the level of prosperity and personnal freedoms will likely be closer together. I think that will also depend on whether the US will renew the Defensive Pact ended in 1980, guaranteeing nuclear deterrence. But the way Trump handled South Korea is not really encouraging for the Taiwanese people to believe in a long standing reliability of that.
To the key question:
but would the Chinese really risk global war just to maintain their sphere of influence?
I don't think China will react on the short term with a real big war.
They cannot have war militarily any time soon..... they cannot have war because they need the sea passage through the South Chinese Sea for their maritime Silk Road.
The question is for me really: what does the US really gain by big Taiwan moves ?
Smaller reversible moves, as are already happening the last two decades and at higher rate since Trump, would fit good enough in the trading war ?
Taiwan as such is only a loss of face for China. Hindering the maritime Silk Road more effective.