Well, it's hard to bring about a national liberation front in Iraq, and by no means do I believe that Sadr will necessarily succeed.
But diversity in itself is not an insurmountable obstacle. Iraq is less ethnically diverse than Iran and less religiously diverse than Lebanon.
Iraq: Demographic information from the 2006 edition of the CIA's The World Factbook [16]: * Ethnic groups: Arab, 75–80%; Kurdish, 15-20%; Turkoman, Assyrian or other 5%. * Religions: Muslim, 97% (Shi'ite, 60-65%; Sunni 32-37%); Christian or other, 3%. <http://en.wikipedia.org/wiki/Iraq#Demographics>
Iran: The major ethnic groups and minorities include the Persians (51%), Azeris (24%), Gilaki and Mazandarani (8%), Kurds (7%), Arabs (3%), Baluchi (2%), Lurs (2%), Turkmens (2%), Qashqai, Armenians, Persian Jews, Georgians, Assyrians, Circassians, Tats, Pashtuns and others (1%). . . . Most Iranians are Muslims; 90% belong to the Shi'a branch of Islam the official state religion, and about 9% belong to the Sunni branch (many of them are Kurds). The remainder are non-Muslim religious minorities, mainly Bahá'ís, Mandeans, Zoroastrians, Jews,Hindus and Christians. <http://en.wikipedia.org/wiki/Iran#Demographics>
Lebanon: No official census has been taken since 1932, reflecting the political sensitivity in Lebanon over confessional (religious) balance. It is estimated that about 40% are Christians, 30% are Shia Muslims, 25% are Sunni Muslims and 5% are Druze[15] There used to be a small minority of Jews, mostly living in central Beirut. Also, a small community (less than 1%) of Kurds (also known as Mhallamis or Mardins) live in Lebanon. . . . 360,000 Palestinian refugees have registered in Lebanon with the United Nations Relief and Works Agency (UNRWA) since 1948, estimates of those remaining range between 180,000 and 250,000. <http://en.wikipedia.org/wiki/Lebanon#Demographics> -- Yoshie <http://montages.blogspot.com/> <http://mrzine.org> <http://monthlyreview.org/>