Of Popes and Tyrants and Hedgehogs
Western religion is politics - this is why American right-wingers(motto: Jesus died so we can be jerks) proclaim that "America is a Christian nation" - because they see Christianity as a political force instead of a spiritual force. (the word "nation" as opposed to country or state is also interesting because it involves the implication of homogeneity) The situation in part of Africa and the Middle East are clearer with Islamic states - there Islam is the law, the government is the ruling class's Islam and therefore Islam is politics. Christianity was the same during the supremacy of the Catholic church - the pope was head of Catholicism and political head of Europe. I'm omitting Judaism because there hasn't in more recent times been a theocratically controlled Jewish state though I assume it would run into the same issues. Nor do I rule out non-Western religions that are similar in nature to Western ones.
Politics determines the structure of society and who controls it. During the creation of Islam and Christianity, the most familiar form of government was totalitarian which partly explains their setup. In Christianity, God is a king, Jesus is the prince, saints or angels or apostles are the nobility and everyone else is a peasant. The focus in Christianity is that the king makes the rules, the peasants blindly obey and exist to serve the king. Such a worldview co-existed naturally with absolute monarchies of the time, especially when the king of a state declared himself to be chosen by God and therefore part of God's nobility.
However, integrating the Christian worldview with democratic government is more problematic. Democracy is rule by the people, the ruling class responds to the will of the people who decide what the ruling class should be - it is completely at odds with the Christian form of government. To apply democracy to Christianity is to say that God must respond to what the people want, that God exists to serve the people, not that people are God's anointed slaves. The founders of the United States explicitly formed a democracy, a democracy that included freedom of religion therefore it could not have been their intent for the United States to be a Christian monarchy. Christian government necessitates a totalitarian structure and cannot exist in a democratic state. The only question is whether the people still will a democracy - if not, may almighty God(s) please turn me into a hedgehog.