I think shortening the American Civil War article would make it worse 
The subject matter makes it difficult, if not impossible, for the article to be adequate in covering the major topics if it was shorter, due to the nature of the subject matter. There are already a lot of sub-articles on the Civil War. Also, every attempt was made to be concise and leave out filler to begin with. I don't know what you could take out that would be an improvement, as opposed to the opposite.