The first civil simmered for many years before it erupted into violence and then war. Emotionally it was about slavery but economic problems played a huge role. If things get bad enough, especially in conjunction with the decline in our culture, not to mention stolen elections, don’t be so sure it won’t happen again.
He’s wrong about civil wars happening either in democracies drifting towards dictatorship (that’s the US, alright) or in weakening dictatorships (Balkans). The first civil war was nothing like either extreme. It was its own complicated mess bearing no resemblance to his models.