The Minie Ball was invented in 1847, but didn't really come into use here until about the time of the Civil War. It was apparently used in the Crimean War a decade earlier, but we don't really get into wars like that in our education system. Buy, yeah, I would put the Minie Ball down as one of those developments that had a huge impact. While it was a pretty short lived innovation due to the subsequent development of the metallic cartridge, it proved that rifled weapons had an important place on the battlefield compared to smooth bored muskets.
As far as the American Revolution is concerned, the rifle was more of a niche weapon. It absolutely made a difference due to colonial sharp shooters and such, but muzzleloading rifles are slow to reload and not much use in the frontlines of battles as they were fought at the time. They are a blast to shoot and hunt with however. These days I find myself more and more wanting to hunt with my flintlock rifle and decked out in historically accurate clothes and stuff just because I'm a weirdo who likes to get back to my roots and do things the way my ancestors did things when they settled Mexican Texas.