Answer:
The United States had home turf advantage, they knew the land something the British did not know.
They also had good military leaders such as George Washington, leading them throughout the war.
They had help from the French. The French not only helped finance the war, but put their own soldiers in the war. They were looking for revenge against England for the French and Indian and thought this would be a good way to act on it.
The United States also had military experience from the French and Indian war, which helped prepare them for the revolution.
There are more reasons but these are the ones off the top of my head.
Explanation:
