A few depressing points, if I may?
1. The issue isn't really about the entire US population becoming One God Apostolics. As awesome as that would be, that's really not the issue. No nation has been perfect. Of the Seven Churches in
Revelation 2 and 3, how many were 100% in the will of God? Most of them were full of either backsliders or heretics. And those were apostolic churches! The issue here (in the thread that depresses PressingOn, one of many) is that AS a nation adheres to the Word of God, there is a corresponding blessing. If the nation seeks guidance from the Word, it is a student of God. As individuals we convert and become students, we learn, we grow, it is a process. A nation is no different, there is growth and learning. Hopefully the society becomes more thoroughly submitted to Christ and His Word. That is in fact the church's job: to disciple the nations.
2. Much of western civilisation is based on God's Word-Law. The common law which gives rise to American jurisprudence is largely just applications of the Bible to various situations. Ask yourself, "Would gay marriage be possible in early 19th century America?" Obviously not. Why? Why would it have been illegal and unrecognised by any state, court, or federal officer? Because it was UNBIBLICAL. That would be the legal reasoning that would have been used to reject a gay marriage agenda. The Christian and Biblical history of our nation is for the most part completely unknown even to most Christians. There's a reason car dealerships in Texas cannot be open for business both days of the weekend. It's a last remnant of the old blue laws. Which prohibited businesses from operating more than six days a week. Why? Because of the fourth commandment. Sure most of them were wrong about which day it was, but the fact remains: conformity to God's Word was a primary foundation for LAW in the US.
3. Render to Caesar... What exactly is Caesar's property? People use this all the time to excuse bad government. It is not Caesar's right to prevent obedience to God. Never was and never will be. Jesus' words do not mean "Government sucks so make sure you don't even think about improving it."
4. Separation of church and state originated as a baptist doctrine in the 1600s. It was co-opted by masons and humanists to make a way for them to infiltrate and subvert Christian society. Separation of church and state is a slogan that really means "Christianity should have no influence on policy." It is the cry of the antichrists as they subvert the state and institute THEIR religion as public policy.
There is no such thing as religious neutrality in politics. All politics is the application of some particular religious view to the governance of society. So which religious view should guide and inform policy? Which is better for the people? Should policy be guided by ungodliness? Or would it be better for policy to be informed by God's Word?
As a Christian, wouldn't you want society to get its direction from God and His Word? Wouldn't that be BEST? So then shouldn't we as Christians be pointing everyone to Christ as Saviour and Solver-of-problems, and His Word as the "instructional manual" for human society?