Separation of church and state is simply an impossibility, unless of course you imprison all Christians in the United States or otherwise forbid their participation in government. It is ludicrous to think it can be done, and conniving to attempt to make it so.
Biblically, the word church (Gr. ekklesia) means "called out". The church of God are those who the called out of Jesus Christ. The church of God is people. There are only two other categories of people in the Bible.
When they say "separation of church and state", they are saying "separation of Christians from government", or they simply don't know what they are talking about. I'm fairly certain the US Constitution would have never been ratified by any state if that is what was intended. There are obviously those throughout our history and still today who would like for it to be the case. They are, of course, either unqualified for public office, or worse, liars, thieves, and idolators. How is it possible that any of them hold or have been appointed to public office?
For those with any sense or intellect, it is easy to see that the founders of the nation wanted separation of denominations from the state. There was to be no denomination that would have the run of the federal government. That seems like a pretty good idea, don't you think?