The country's spiraling militarism – trumpeted this week in missile tests and military maneuvers – plus its influence in Iraq and its controversial president, appear to be making some Arab states more nervous that there could be future menace in Tehran's ways.
Now, we know Iran is trying its best to obtain nuclear weapons. The Arabian Peninsula nations do not want that to happen anymore than we do (and I would urge them to forget about trying to make the Mideast Nuclear free in an attempt to disarm Israel, this is being too clever by half) as Iran would get even more pushy.
Now, Iran's trump card is it can easily shut down shipping going in and out of the Persian Gulf and can make shipping difficult all the way out the Indian Ocean. Of course, we would not allow for that but it would take some time to take care of. Of course, everyone thinks "Oh no! The world loses access to oil".
Again, I am confident the US will be able to keep those shipping lanes open. However, it will not take too much to scare up the price of oil both in terms of the futures market and causing tanker insurance rates to go up. The demonstrations Iran has been putting on have little to do with defense but much to do with scaring the oil markets. The majority of the weapons the Iranians have been showing off to the world are anti-ship weapons.
I would be quite certain the moment Iran decides to shoot it will be shooting oil tankers not USN ships. I wonder what percentage of tankers leaving the area are shadowed by Iranian subs.