Secession is the real elephant in the room. I think seceding states that did away with a Fed and legalized, say, silver for every-day transactions would have a great competitive advantage over countries that just kept producing more Monopoly or digital money. Also, the seceding states might decide they don't need a massive military to protect them from future invasion by Iran or North Korea or even Russia or China. Economic realities will change everything at some point. This said, big wars remain the greatest worry as they tend to happen in times of massive economic strife.