You fundamentally misunderstand the difference between tactical and strategic nuclear escalation. You are not signaling that the next step is MAD if you go for Hawaii. Going for Hawaii itself is already a MAD trigger.
No, you are falling into the logical fallacy of western ‘tactic’ nuclear bullshitary where they arbitrarily draw a line on what kind of nuclear retaliation is ‘acceptable’.
China has never signed onto that idiocy and never will. As far as China is concerned, nuclear weapons are nuclear weapons. There is no distinction between tactical or strategic weapons. You use nukes against China and China will nuke you right back. It doesn’t matter if you use puny tactical yield weapons, you are still eating megaton Chinese strategic nukes back in response.
This is why China has to nuke unquestionably American soil as a first response, to shatter all the logical fallacies western strategists and leaders have surrounded themselves with. Otherwise American leaders will continue to cling onto those fallacies and order more escalatory strikes against China thinking there is some magic threshold China will not dare to cross. That’s how you stumble into MAD.
And glassing Hawaii will not trigger MAD. You think America is going to see a handful of ICBMs heading to Hawaii and press the ‘reply all’ button? No. They are going to wait until those missiles land to make a decision because they can afford to wait and see before acting since their second strike capabilities are not at risk.
It’s when you see hundreds or even thousands of incomings that you are forced to respond before you can know the nature of the attack because if all those incomings are nuclear, you don’t get to strike back. That’s precisely the predicament China will be facing if the US crosses the nuclear threshold in any way. It’s one thing to deal with thousands of incoming US conventional cruise missiles, but how can China trust that all or even any of them are conventional if the US already used nukes?