However, assuming the US gets away with this diplomatically, this does set a real precedent that countries can get away with this diplomatically; which will make it harder to organize diplomatic and economic responses to China.
If not: Is Trump really willing to make it happen? Is Congress willing to let him? And at what body count? (Even if you're only counting American bodies, it won't be zero...)
You missed the referendum? Hm. So did I.
Ultimately, the international rules based order was mostly created to protect smaller and weaker powers that be and to constrain the strong. Since nobody can enforce international law, the strong do what they like anyway.