Ross Douthat's New York Times write-up this morning, I'd like to offer 5 reflections I've noticed in reading world history:
1) Wherever Christianity has spread, the social conditions for women and children, the poor, and the under-educated have improved. (This occurred in pagan countries in the early middle ages, post-communist countries in the 20th century, and in Islamic countries in the late 20th and early 21st centuries.)
2) At some point these cultures and countries impacted by Christianity quit relying and seeking direction from the Christianity. They begin to trust in the people who have benefited from Christianity (now post-Christian "elites"). The post-Christian elites hold to a remnant of Christian teaching (albeit many reject Christianity altogether), but have often abandoned its core doctrines of orthodoxy. This is most evident in European cultures. They perceive Christianity more as a springboard onto something bigger than as the foundation that should never be abandoned.
3) In time, the social conditions begin to deteriorate for women and children, the poor, and the under-educated. This would be seen in the increased percentage of children born out of wedlock, without both parents involved in their lives, and the necessary government involvement to provide basic necessities and education (and sadly, many of these investments in the children still do not prevent a high crime rate and unhealthy life choices).
A desire for "upward mobility" is not motivating enough for many. Likewise, when Christian convictions and morals are lost, most people lack the drive and inward motivations to properly deal with a decaying culture. People are not willing at any fundamental level to sacrifice and serve those most in need. Voting for higher taxes and increased government support (the common answer in more liberally-minded elites) has not solved our social conditions (and possibly has made them worse for some).
4) Both non-Christian and previously Christian empires and countries have shriveled and died, rising out of the ash heap as military-regimes, hostile government takeovers, mob states (some led by government officials), and the like.
5): What beliefs and convictions lie in the heart of rulers and followers has a large impact on its future. These will dictate the next direction a nation turns.