The American Civil War
Now that we're covering the American Revolution, the next logical place to take games is clearly the Civil War. Real time strategy titles like Sid Meier's Atietam and Gettysburg have gone there, but it would be great to get a perspective on events that's not isometric.
The Civil War is one of the most dramatic and important periods in American History, and a game in which you take control of a Confederate or Union soldier on the front lines (literally; everyone stood in lines taking turns shooting at one another) could bring that to life better than any text book or documentary. On the other hand, we'd be just as happy with Abe Lincoln: Vampire Hunter: The Video Game.