The US has local oil extraction so in theory its oil supply should be easily self-sustaining. Of course oil doesn't work like that (the local refinement industry is not built for the domestic oil) but this failure is ultimately a consequence of economic policy - not that the US is unique in this.

As I understand it, the oil reserves simply weren't built for frequent use. They were built as a backup plan for a global supply chain collapse. Arguably that happened twice in recent history - first with COVID, then with the US deciding to do it itself by getting into a war with the one state where its experts had predicted a war would cause this to happen and that could not readily be defeated because it's literally carved into a vast mountain range and had decades to come up with a plan for defending itself.

Honestly, the war on Iran isn't even in the range of ordinary American politics - even if you come from the most pessimistic "CIA regime change world tour" angle. There's no coherent reason for it to have been executed the way it was that doesn't require assumptions that most people justifiably would dismiss as conspiracy theories (e.g. intentional destroying the global economy for short-term profit through betting & investments).

It's noteworthy that the caverns holding the reserves are on the verge of collapsing. But it's kind of a moot point because there's no way to restore global supply lines in time to refill them when fully drained this time. Tankers are the only viable way to transport large amounts of oil over long distances and it would take months for any shipments out of the region to arrive and there have been practically no shipments for months already.

Unless the US is going to enact rationing, reserves will be gone soon and so will be local supply. Plus if there's any place willing and able to buy oil at a ridiculous markup, that's where the market (and the remaining supply) will go unless the US wants to pivot into outright piracy.