I think you underestimate how much of that 50% is just exports. And how much other plants can be scaled up quickly. And how the US can temporarily nationalize things, and ensure all the output goes domestic. Just a backroom threat of emergency, temporary nationalization, would ensure CEOs give the US priority.
IE, they'd get to retain higher profits.
What I think would really happen, is the rest of the world would suffer and run out of energy. Not the US.
There's no think, this is know territory.
Gulf coast PADD3 refineries = disproportionate production of diesel, aviation, bunker fuel for CONUS use. Something like 70% of all refined products used in US comes from PADD3, other refineries cannot replace PADD3 complexity/production levels (think specialty fuels for military aviation, missiles etc). US economic nervous system is EXTRA exposed to gulf coast refinery disruptions. PADD3 refineries (or hubs / pipelines serving east/west coast which more singular point failure) itself enough to cripple US with shortages even if all exports stopped. Gulf gas terminal is for export i.e. doesn't materially impact CONUS, it's deterrence conventional counter-value target. There's also offshore terminals. The broader point being gulf coast has host of targets along escalation/deterrence ladder.