I met a chap today who was browsing the American Civil War books in the shop where I work. He was a re-enactor, but he said that English Heritage no longer hire American Civil War groups for events.
So what's the American Civil War got to do with English history?
Quite a lot, as it turns out, and this chap knew an enormous amount about it. There were the 179 ships built in Scotland for use as blockade runners to provision the South, for instance. Meanwhile, (something that I knew) Lancashire cotton mill workers were refusing to handle cotton from the American South in solidarity with the slaves. "Liverpool grew rich while Lancashire starved," the chap said. There was even an incident where a British ship was captured by the Union navy - which should have been an act of war, but Britain didn't have enough troops, and couldn't get troops to Canada quickly enough, so it was all smoothed over. If Canada had joined in the war, there could have been a very different outcome - Britain might even have got some of the Colonies back! (Or the Union could have conquered Canada!)
The French got involved - Napoleon III sent troops over to Mexico, though in the end it didn't help France, as the Mexican Civil War started just after the American Civil War ended.
So the American Civil War had serious repercussions in the British Isles - it's not just a foreign conflict that had nothing to do with us, so it seems quite reasonable to have societies re-enacting it.