When people say the US should be a "Christian nation," they never mean that we should feed the poor, clothe the naked or, God forbid, turn the other cheek.
What people usually mean by the term "Christian nation" is that their own primitive ideas of creation should be imposed upon science classes and that their almost perfect ignorance of human biology should become law. Unlike Peter, many Christians only lay down the sword so they can take up the gun.
If by "Christian" people meant "followers of Jesus" they might be surprised to find that we would not have to shape others into our own image. We could work with them as they are to make this a better world. A follower of Jesus, and of Buddha and of Darwin would each bring something to the one task that Jesus called us to- calling the world to love.
Rules, beliefs and rituals are never the heart of true religion. A religion what does not dissolve into love is like food that has not properly digested. What calls itself "Christianity" is, often as not, a bad case of spiritual indigestion.