If one wonders how America became a superpower, one needs to study its history, and especially its battles. Foote's trilogy is massive in scope, and considered one of the eleven best works on the Civil War.
http://www.thedailybeast.com/article...civil-war.html
Non-Americans may wonder why we continue to be fascinated by a war that ended a century and a half ago. It was a war where the winning side was perceived to be the one in the right (at least morally). The subject makes me wince. It is very touchy in some circles, and not the kind of topic you discuss in a friendly debate. But if anyone wants to know why Hitler and Hirohito were destroyed in WW 2, the answer is that America managed to stay "one" nation after the Civil War, despite our many disagreements, which persist to this day.