There were a number of factors that allowed the American colonies to win the Revolutionary War.  Let us look at some of the more important of these factors.

• Greater motivation. The colonists really wanted independence while the British were not nearly as motivated to prevent the colonists from gaining independence.  In addition, many of the British soldiers were not enough British. This reduced their motivation even further.
• Easier logistics. The colonists were fighting on their own home territory and could more easily get supplies that they needed from the people.  The British had to move supplies and personnel across the ocean.
• Foreign diplomacy. The colonists got the support of outside powers, the most important of which was France.  This helped them with the money and supplies needed to fight. Military support from France was also vital at the Battle of Yorktown. 
• Fewer distractions. The British had to worry about maintaining their strength around the world.  They could not pour all their resources into the fight against the colonists. The colonists had no concerns other than fighting the British.

All of these factors helped the colonists win their war for independence.