It'll be like the annexation of Crimea. Biden could just say that under the One China policy, the US has no business meddling in "internal affairs." A military confrontation requires a strong leader to say, "no, fuck you!" Biden is highly susceptible to bribes and is a doddering old man that broke his foot chasing a dog's tail. Also, the average American doesn't understand or more importantly care about foreign affairs. Unlike the military, they don't want to be involved in ANY wars. To them, China attacking an ally doesn't mean anything to them. Notions about defending Democracy are 100% cringe and gay.
So, I have to politely disagree. It's easy to get the Biden administration to do nothing. Especially since it will improve his relationship to the CCP at the same time.