When I was first learning about the American Revolution, the rifle was touted as this war-winning weapon that gave us the needed edge over the British in order to win the war. While I now feel that that is an exaggeration, I was curious how much of an effect rifles actually had on the war.
There were as yet no "rifled muskets": that term would come later in the 19th c. There were instead smoothbore muskets, and rifles.
There was a pretty good discussion of a similar question here a while back. Certainly, to claim it was just the Americans' use of rifles that won the War is wrong. The important things were French aid ( including guns and gunpowder) , Washington's ability to keep an effective army in the field able to take advantage of opportunities but avoid getting crushed in a pitched battle, the inability of the small British army being able to occupy and secure much territory in a huge rural landscape, and the low priority placed by the British government on winning the conflict, crushing the rebellion.