As an ACW buff who is also a "nerd" in the more traditional sense, I do have to admit that seeing all those Marvel Civil War books *do* throw me for a loop.
If you'd said "Civil War" to an educated person of the 1860s, my bet is that they would first think of the Roman Civil War first, and then possibly the English Civil War after that.
Living in the USA, nothing makes me cringe quite as much as the closing words of the Runs N Roses song "Civil War" when Rose state: (and its so absurd I could not make it up), "...what so civil about war anyways".
I agree with that, and it still does. But were those other wars the first thought on educated people's minds, in the midst of a domestic civil war? That's what I doubt.