Even if the majority of Americans are not practicing Christians their interrelationships are still based on that tradition. No there is no Atheist morality, just about by definition. That does not mean that an atheist does not share the same ideas as Christians. For the Christian morality is of God and he can't change the system. He can evade it or oppose it but he can't change it. For the atheist there is no such thing. He can determine with his reason what are the most useful relationships for how he wants to live. He may use the word but it is not the same word when he does. In a Christian or other religious based society the atheist is stuck with the morality of the dominant culture.In a Communist state there is no morality because social requirements are arbitrary and capricious. They change with the perceived requirements of the boss. "Morality" is what seems beneficial right now by the ruler. Communist rule is just oldtime absolute monarchy without the perceived legitimacy.