The separation of church and state seems to be one of the most misunderstood aspects of our country. Let's look at the actual words for a second.
"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof..."
What does this actually say, and where did "separation of church and state" actually come from?
What the first amendment actually states is that congress will stay out of religion. Nowhere does it say that religion should stay out of congress. It says that there will not be an official religion of the US, or any laws restricting religious freedoms.
To say that the US as an entity is "one nation, under God." does not cross this line as there is no law passed to enforce anyone to actually believe in God. There is nothing stating that we can't display the ten commandments in a court, just that we can't enforce them as our own laws. (which kinda makes it pointless to put them in the courtroom, but it's still legal.) There is nothing stating that we can't have public prayer, we just can't force people to participate in it. There is nothing stating that we can't have God on our currency, we just can't make people swear by it to spend that money. This country has freedom OF religion, not freedom FROM religion.