[ceejayoz]

The Navy was present during every incident listed on https://en.wikipedia.org/wiki/Strait_of_Hormuz#Events, including seizures of oil tankers and cargo ships. Minefields are also a handy option. Iran can and has disrupted traffic through the strait; it's an effective threat even if they can't keep the US Navy out.

[bayesian_horse]

Yes the Iranian Navy can pester a commercial ship here and there. They can't blockade the entire Hormuz street and even if they ramped up those seizures too much, they'd draw an international response they wouldn't like. Iran can't want a shoot out with the US in any form...