The people are what makes the US Military so effective. No one has a military trained like we do. The sailors on those ships have nerves of steel.
From a strategic standpoint the Iranians shooting at the Arleigh Burkes is more harassment than any real attempt to sink them. They have the ability to do that should they choose to, but they know what would happen if they crossed that bridge. They have thousands of missiles produced on the designs of old French Exocets and Chinese Silkworms. They're accurate and deadly and absolutely can get through defenses in a massed attack. We used to joke the Exocets would give a dolphin a haircut if one happened to breach in the missile path. They're still detectable skimming over the sea surface but less detectable than something above the horizon.