It doesnt affect US supply as much as Asia's, however it affects oil prices. $250-500 for barrel would choke most World economies, including US.
If Iran oil is under full embargo, that means China and Russia didnt veto such resolution in UNSC, therefore they know whats coming.
Whats concerns Iran, if World bullies want to choke Iran completely, Iran wont stand and watch, but rather grab bullies by the balls, even though there is a huge disparity in power. Iran leadership does have a steel cohones.
Closing the Gulf (and probably exploding Saudis/UAE pipes) will absolutely be a turning point, "cease and desist" of all nonsense sanctions against Iran altogether. Either World will come to its senses, or there would be WW3, either way it will be resolved.