The American Colonists only won the Revolutionary War because of four reasons.
1. France
France supplied the American Revolutionaries and had ships rival the British fleet. France played a crucial role in blocking off Yorktown's river so that British reinforcements couldn't get into Yorktown to help the surviving British soldiers.
2. Guerilla Warfare
This means that regular citizens in the colonies got arms and just started shooting redcoats. These people were called Minutemen because they could get ready for a battle in a minute. American colonists rose up and arms to fight off the British for freedom.
3. Knowing the Terrain
One of the main reasons Britain lost their colonies was because their soldiers didn't know the terrain as well as American colonists. Back then, America was mostly trees so redcoats had to go through dense forests. Because of the forests, the raid to cut off New England colonies from the rest of the colonies was a failure, American snipers picking off soldiers, native guides, and even generals. Great Britain also was used to fighting in open terrains so their formations didn't help them in these forests.
4. Britain Arrogance
The monarchs in Great Britain thought the war could be won in a day so they didn't really prepare for a very long war. When they finally realized that they couldn't win quickly, they had to rely on German soldiers that they paid to work for them.