I also say that various philosophical, social, and professional systems of ethics have always existed side by side with religious systems of ethics, except where religion outlawed such systems, and of course where such systems in effect outlawed religion. Equally, I do not agree that most Marxists derive their ethics from any perceived needs of the working class.
And finally, I say that "eclectic personal ethics" are not only the most common, but are almost unanimous source for ethics in America today, yesterday and all the way back to our countries founding.
Regarding eclectic ethics, you are right that in America today many and maybe most would not consciously trace their morals to Christianity. But few behaviors contradicting the Christian ethics are viewed as ethical (much more are practiced as an ethical weakness, e.g. various transgressions from the Christian marital code of ethics). Historically, the cultural makeup of today's Americans has been shaped almost exclusively by Protestant ethics of the First and Second Spiritual Awakenings, that gave America its Revolution and its Civil War. If religion were not pushed from the public view by the secularist minority, we'd have more recognition of the Christian roots of common ethics.
Rand, however, is outside of the pale of Christian ethics, primarily because of the issue of kindness that we've been discussing. So I'd say that while an American who is unaware of Rand may be equally unaware of historical Christianity, his ethics are of Christian roots; and an American sympathetic to Rand's ethical teaching would have to reconcile the traditional ethics with Rand's and would come up with an eclectic system.