The majority of Americans think that theirs is a "Christian Nation." Many Americans are indeed Christians, and many citizens who hold this view belong to the Religious Right that believes in social conservatism. Wikipedia says that social conservatism "is a political or moral ideology that believes that government has a role in encouraging or enforcing what they consider traditional values or behaviors."
Some liberals think that the Religious Right is out to do one thing: overthrow Roe v. Wade. This may be true, but let's take it one step farther. In what-if situations like this, I often take the outcome to more of an extreme to see if this really is a slippery slope.
Let's take the Reconstructionists. These militant Christians essentially want to throw away the Constitution and replace it with Old Testament law — basically making themselves into the American Taliban. Reconstructionists believe that if we don't follow God's law, then all cultures on Earth will self-destruct. They also believe in Postmillennialism, a Christian eschatological belief that God's kingdom began at the first coming of Jesus Christ, and that it will advance progressively throughout history until it fills the whole Earth through conversion to the Christian faith and world view.