The Holy Roman Empire wasn't holy, Roman, or an empire.
I'm studying this right now and it actually was to a large extent all of those things after Christ died. Constantine saw to that. I am absolutely floored at the role Christianity played at preserving knowledge, culture, and human life through the 'dark' ages.
What is so striking is how divorced America and Europe has become from Christianity culturally and politically.
After William the Conquerer, the Papacy became more corrupt, helping to make permanent the schism between the Eastern Orthdox church, and helping to instigate the Reformation.