I think the point of civil wars being damaging is spot on, but the example of the Thirty Years War as a civil war is quite flawed: The Holy Roman Empire had alw

I think the point of civil wars being damaging is spot on, but the example of the Thirty Years War as a civil war is quite flawed: The Holy Roman Empire had always been a small aggregation of city states, as you call it. The position of emperor held some political power, and attempts to centralize into a state were made a few times (Most significantly with the Reichsreform of 1495, which could not be enforced), but ultimately, the Holy Roman Emperor was one noble among many, with the rest of the empire paying him nothing more than lip service. And a detail: Bismarcks Prussia didn't reunite the HRE, it formed a nation out of most of the culturally German parts of the former empire (which had been dismantled already during the Napoleonic Wars), notably and among others missing Austria since they were historical rivals.