Persia and the power vacuum

By focussing on Iran's Shia Muslim religion it seems that many of us have been missing an important point. Just as the Sunni Arabs had an Empire that stretched from India to Spain, so the Persians had an Empire that stretched, not quite as far, from India to Egypt. Especially the Sassanid Empire (not to be confused with the Sassenach Empire), that had as its state religion Zoroastrianism (still lingering on as the religion of the Parsis of India), that lasted from 224 to 632 ce and was swept away by the Arab Muslims. The Persians, or Iranians as they called themselves, then opted for the non-orthodox Muslim faith of Shi'ism.
Nevertheless, many Iranians remember the historic extent of Persian power, and relish the idea that they are once again being expansive and flexing their muscles. Of course, the Imams in Iran would never admit this, since any history before Mohammed is considered unholy, but to ordinary Persians this is a factor. For example, the Iranian American woman who went into space as a tourist a few months ago, although completely secular, said that she wished to dedicate her experience to the greatness of the Iranian people.
There is a power vacuum in the Middle East due to the overthrow of Saddam Hussein, the strong man of Iraq and of the central Arab world. Remember that the Iranians and Iraqis fought an 8 year war for control of the area, and the war ended in stalemate. But the US has been unable to fill this vacuum and has been unable to replace Saddam with a strong democratic Iraq, in an area where democracy is unknown and untried. Since the US has evidently failed to control the security situation and insurrection taking place in Iraq, this counterweight to Iranian power has been removed. The assumption that a unified Iraq would replace Saddma's Iraq as a counterweight to Irna has not transpired. This assumption not only neglected the weakness of Arab democracy, it also ignored the over-riding hatred between Sunni and Shia in Iraq. It seems there is no way that they are going to be contained in one state, short of a ruthless dictator such as Saddam.
As a consequence, the Iranians have been helping the Shia Arabs in Iraq to throw off the yoke of American and British imperialism as well as Sunni control. As the US has appeared weaker the Iranians have appeared stronger. Now they are boasting about their nuclear program (read weapon) and are seeking to fill the power vacuum left by the overthrow of Saddam's Iraq and of the US as the most powerful country in the Mideast. Iran has already co-opted as part of their sphere of influence ("empire") Assad's Syria and the Shia Hizbollah of Lebanon
Since the US is in withdrawal mode in Iraq ("let's ask the Iranians and the Syrians if they'll help us??") and now seems reconciled to Iranian hegemony, who does that leave to stop this Iranian drive for power? The only potential counter to Iranian power now is the combined Sunni power bloc. Given that Sunnis outnumber Shia by a factor of 100:1 in the world and probably 10:1 in the Middle East, and includes such countries as Egypt, Saudi Arabia, Turkey, Jordan, Pakistan, etc., one would think that a Sunni coalition would arise to oppose Iranian expansionism. That is happening, but oh so slowly. The Sunnis prefer to buy off their opposition, as they have been doing for a long time with the Palestinian terrorists, and they are suspicious of each other's motives. So no serious opposition is likely to cohere from the Sunnis until it is too late. And who does that leave, you are right, little Israel!