Sorry, what part of the US is based on purely Christian values?
Dont get yourself confused between a Christian majority nation and a Christian Nation.
Majoriy doesn't rule.
Any power the majority receives is given to them by the law, and that law prevents majorities from imposing their religous beliefs onto the national identity.
If you notice something good in yourself, give credit to God, not to yourself, but be certain the evil you commit is always your own and yours to acknowledge.