Sorry, but the history of technology is one of my things, and I think that there’s a misrepresentation going on here about how technology develops. Not only is it rarely mono-causal, it’s extremely rare that one cause even predominates in the evolution of a technology (such as a railway system). I don’t think it’s the case that 20th century conflicts have remotely a large enough impact on the development of the European railway systems to properly explain why it is that they aren’t more integrated.