The colonists were familiar with the terrain of the land where they fought. They lived there, so they knew the best places to hide, where to shoot, and what the more strategic locations were. The English troops didn't have this advantage.
The tactics used by the colonists and English were of importance. The English marched in formation, and were trained soldiers. The colonists, on the other hand, weren't trained soldiers and didn't march in formation. They practiced guerilla warfare, that is, they stung the British, ran away, then stung the British again. The British in their formations made easy targets, while scattered colonists behind trees and walls did not.
Also important were the alliances the colonists formed with foreign nations such as France. At the Battle of Saratoga, the colonists proved themselves worthy of help, and nations like France sent troops and supplies to help the colonists.
The fact that England had to send troops and supplies thousands of miles across the ocean to fight the war also played a role in the colonists' victory. England was spending a lot of money to send troops across a dangerous ocean. And the great distance left England unaware for weeks what developments in the war were.
Several key factors made an American victory possible in the war for independence. One was the familiarity with the terrain. Another was the differing war tactics. The alliances with foreign powers was another. Still another was the difficulty for England to send troops and supplies across a vast ocean. These factors enabled the colonists to win independence from England.