I think a religious nation is a bad idea. When religion becomes a requirement of citizenship, or when religious authorities gain political power (not influence because that is a different issue altogether) it creates conflicts of interest. .
Robert Heinlein once said that man is arationalizing animal; instead of looking at the evidence and making a decision we have a habit of making the decision and looking for an excuse to do what we've already decided to do. And let's be honest, God is the perfect excuse for just about anything you can think of."I voted against the bill because its clearly what God wants me to do, and as a christian I always follow God's will."
"Yeah, and the fact that your stock options would be worth less than half what they are now if the bill passes has nothing to do with your decision?"
This applies to Christians as much as anyone else and as someone who has always considered themselves a christian I would argue that the idea of a Christian Nation would go against Christ's teachings. "Render unto Caesar that which is Caesar's, render unto God that which is God's" meaning that politics and religion are different things and should not be confused with one another.
This is why anytime I hear people talking about how the USA is not longer a Christian nation I want to roll my eyes. Maybe we are not a christian nation because never truly could be such a thing, or maybe we stopped being a christian nation because we can't tell the difference between God and Caesar anymore.
(I'm not trying to pick a fight with anyone I felt like I needed to get this out there.)