How would the USN react to the sinking of a Nimitz class carrier? Tactical Nukes? Strategic? Whatever it is, such an event would precipitate an all-out, no-holds-barred attack on Iran and there's no guessing as to the eventual winner in such an uneven contest. You only have to recall the US response to the Japanese attack on Pearl Harbour. They took a lot of time working up the momentum but just look where it ended.