There are people who desire that the USA become a theocracy:

• “There should be absolutely no 'Separation of Church and State' in America.” – David Barton
• “Anybody that believes in separation of church and state needs to leave right now.” – Star Parker
• “The 'wall of separation between church and state' is a metaphor based on bad history, a metaphor which has proved useless as a guide to judging. It should be frankly and explicitly abandoned.” – William Rehnquist, Chief Justice of the Supreme Court of the United States of America (1924 – 2005)

Whose religion? Well Christianity of course, the one true religion:

• “The long-term goal of Christians in politics should be to gain exclusive control over the franchise. Those who refuse to submit publicly to the eternal sanctions of God by submitting to His Church's public marks of the covenant–baptism and holy communion–must be denied citizenship.” – Gary North
• “I don't know that atheists should be considered citizens, nor should they be considered patriots. This is one nation under God” – George Herbert Walker Bush, 41st Presidency of the United States of America
• “I want you to just let a wave of intolerance wash over. I want you to let a wave of hatred wash over you. Yes, hate is good…Our goal is a Christian nation. We have a biblical duty, we are called by God to conquer this country. We don't want equal time. We don't want pluralism.” – Randall Terry
• “Our goal must be simple. We must have a Christian nation built on God's law, on the ten Commandments. No apologies.” – Randall Terry

Why?

• “Our culture is superior. Our culture is superior because our religion is Christianity and that is the truth that makes men free.” – Pat Buchanan
• “Nobody has the right to worship on this planet any other God than Jehovah. And therefore the state does not have the responsibility to defend anybody's pseudo-right to worship an idol.” – Joseph Morecraft
• “The best way to insure the earth is never over populated is for sensible and righteous governments to clear all forms of atheism and heresy.” – Robert T. Lee

And then what will happen?

• “Atheistic secular humanists should be removed from office and Christians should be elected…Government and true Christianity are inseparable.” – Robert Simonds
• “When the Christian majority takes over this country, there will be no satanic churches, no more free distribution of pornography, no more talk of rights for homosexuals. After the Christian majority takes control, pluralism will be seen as immoral and evil and the state will not permit anybody the right to practice evil.” – Gary Potter

But what about democracy?

• “The Court, by seeking to equate Christianity with other religions, merely assaults the one faith. The Court in essence is assailing the true God by democratizing the Christian religion.” – John Whitehead
• “Democracy originated in the mind of a rational being who has the deepest hatred for God.” – Robert T. Lee
• “Do you realize that the only thing that gives democracy existence is sin? The absence of democracy is perfect obedience to god.” – Robert T. Lee

And what about personal rights?

• “Raising your children under Americanism or any other principles other than true Christianity is child abuse.” – Robert T. Lee
• “You do not have the right to be wrong, regardless of what any man-made or demonic charter says.” – Robert T. Lee

So a Christian nation – something a lot of conservatve Christians can get behind. But not just any Christianity:

• “You say you're supposed to be nice to the Episcopalians and the Presbyterians and the Methodists and this, that, and the other thing. Nonsense, I don't have to be nice to the spirit of the Antichrist.” – Pat Robertson

And that's where their dream would turn into their nightmare

The dream of some Christians for a Christian Theocracy in America would rapidly become a nightmare that would make the divide in Islam look like a subtle difference of opinion.

The people who want a Christian theocracy in America are people who know they're right and anyone who disagrees with them is wrong. Unfortunately, they don't agree with each other. Because they could not tolerate the heresy in other churches, they would necessarily have to stamp out apostate churches.

And there are a lot of denominations:

 (see http://www.usachurches.org/christian-denominations.htm)

Imagine the Southern Baptist Convention vs the Church of Latter Day Saints vs the Evangelical Free Church vs the Lutheran Church (Wisconsin Syod) vs the Jehovah's Witnesses vs Seventh Day Adventists vs…

All believing they are the One True Faith that should be in charge of the Christian government – of the USA; of each of the 50 states (I have my bet in on who gets Utah); counties and parishes; townships; villages, towns, and cities…

It would be the bloodiest civil war in the history of the Earth.