On the point of rifles versus muskets. The loading and firing of rifles was slower than the musket. How useful the accuracy of a rifle was in combat on battlefields in wooded country is less clear. The British tactic of firing a volley and charging with the bayonet does seem to have negated any advantage gained by accurate, considered fire from defensive cover.
The later use of rifles in the Peninsular War to bring down officers was very effective, I see less evidence of staff officers being picked off by snipers in the AWI, Patrick Ferguson apart. In the end there appears to have been considerable hype about the American domestic familiarity with arms compared with the British, which would prove less defensible as the war progressed. In the end the American Army only competed militarily on a parity towards the end of the war, stiffened by conventional French units, using tactics developed in Europe.