In the scene were they show the Confederate army camp, if you look closely when they're zooming in to the tent, you will see a corner of the American flag. You can see stars in rows, such as the modern American flag. But in 1776, there were only 13 colonies, and 13 stars in a circle a circle shape on the flag, as shown later in the movie when Benjamin Martin (Mel) is waving it across the battle field.