Britain’s military was much better in terms of supplies and weapons, however Britain had to fight on distant land, which was very costly.
The Americans were fighting on home turf and had superior leadership. And their soldiers had were fighting for their independence, so they had a better reason to fight.
However, they lacked training and discipline. One-third of their people were still loyal to the British. They had a smaller population. They didn’t have the money to afford the basic necessities to support soldiers.