Why did Rome and Byzantium fall apart after centuries of success? What causes civilizations to collapse, from a dysfunctional 4th-century-B.C. Athens to contemporary bankrupt Greece?
The answer is usually not enemies at the gates, but the pathologies inside them.
What ruins societies is well known: too much consumption and not enough production, a debased currency and endemic corruption.
Americans currently deal with all those symptoms. But two more fundamental causes for decline are even more frightening: an unwillingness to pay taxes and the end of the rule of law.