Of course, as soon as I say that I realize the leader of Britain would have been Queen Victoria, and it strikes me as a little odd that both of this expansion's scenarios focus on things that happened during her reign. Considering one of the major focuses of the expansion itself is Ideology (see also: the box art, and the entire expansion's bloody name), why isn't there a Cold War scenario? Forget this nondescript Civil War scenario. Instead, make a whole scenario dedicated to showing off the Ideology system. Have the playable civs of NATO (United States, British Commonwealth, France, etc.) locked into Freedom and the playable civs of the Warsaw Pact (Soviet Union, Poland, China*, etc.) locked into Order. Have them trying to convert all the other countries to their Ideology and fighting proxy wars for dominance all over the world. Make the goal not to be for any one civ to come out on top, but for their Ideological faction. Whichever faction controls more of the world at the end wins, and all the civs in that faction share in the victory. There's your scenario right there.
*No, China wasn't a member of the Warsaw Pact. But it was one of the major Communist powers of the era, so thematically it fits what I'm talking about.