It's about territory for China. According to China, Taiwan is part of China. This is about nationalist pride first and foremost.
-Taiwan only recently extended their obligated military service from four months to one year. Do they have the appetite Ukrainians have to maintain their sovereignty? If not, why bother. Would Taiwanese rather die than live under China's authority?
-Australia and Japan are only now ramping up their military expenditures. Any conventional conflict between the US and China would have them on the sidelines concerned with their own national defense.
-In a conventional war the US would have to attack bases in China which would require a like response from China. Unlike Ukraine, I do not think this is a war that could be contained to just Taiwan.
-Win, lose, or draw, the US military would be devastated and need to be rebuilt.
I think the big question is, would the US be ready to spend hundreds of billions of dollars to defend Taiwan? Would the American people or Congress? I think the answer is no. I think the US would put severe economic sanctions upon China and fight like hell with the EU to go along. The official US policy toward Taiwan is strategic ambiguity. We would use that as an escape from any military conflict. We would build our forces in the Pacific. We are entering into new agreements with the Marshall Islands and Palau and working on Micronesia. I wouldn't be surprised if we reestablished bases in the Philippines.
I think the best course of action for the US would be best to conserve it's military forces and work on breaking China economically. When nations have to decide whether they would want to see economic dominance slant toward China or remain with the US, I think that is the war the US wins every time.