I know there are Christians who would think my understanding of the universality of the 10 Commandments as wrong. But I doubt that many of them want to start putting people in the stocks for using a car or working on Sunday (for instance, Orthodox Jews don't drive or work on Saturday, but don't expect everyone to follow suit).
I think the main importance right now of the 10 Commandments is that people be allowed to express and practice their religion - including the public display of their tenets - and the public discussion of what this country's laws and founding documents are actually based on. (I don't mean that they are based solely on the Commandments but they are to a large degree.)
I don't see that there is any danger of Christianity (as interpreted by this sect or that) becoming mandatory.
Not on a national basis. But on a local basis - a town, a school, a court - it is not only a danger, but a reality.