I suppose that Ben Franklin's friendship with the French King Louis IVX, eventually leading to Frances' committing troops and money to the revolutionary cause, were, in part, responsible for the victory over the better equipped and well trained British army.
Because they were fighting for something they believed very strongly about, they were not forced conscription, and they were able to utilize in large part gorilla warfare tactics of hit and run which was very unorthodox to warfare and fighting strategies at that time.
The french gave their waste (do-do) in a cup which was actually useful. It was useful because it mad them have a stronger force when they added it to their weapons.
The main reason for the victory of the colonists was a disciplined armed struggle. The french also played an important role as they helped the Americans by giving them financial aids. The french navy, though not very strong, used to stopped the supply of British troops to reach the new world. Thus, inavailablity of sufficient British troops when they were badly required in the colony harmed the British crown badly.