A couple people have mentioned the American Civil War and then it was disparaged for only having 2 sides. However, what if the whole continent was involved in the game? Within the Civil War, many tribes were sorting out which side to support. If there were some amount of division by state, maintaining the loyalty of different states could be an integral part of the game. Britain could have also been conceivably involved and traded with both sides to some degree. Russia also sent some Monitors over expressing some support of the Union. Meanwhile, just to the south, Mexico just finished a civil war of their own and was promptly invaded by France which eventually involved Cinco de Mayo among other things. And Spain briefly reabsorbed the Dominican Republic. So it seems there are enough other players to keep it interesting.