The correct answer is the Battle of Saratoga.
The American army proved that they actually had the chance to defeat the British army after their victory at Saratoga. After this battle, the United States would receive help from the French. Specifically, the US would get military expertise from Marquis De Lafayette, a decorated French commander. The French involvement in the American Revolution helped the inexperienced American troops tremendously, as the French taught them discipline, guerrilla warfare techniques, etc
