The revolution was successful because enough of the American public was convinced that it was worth it and they were willing to reach out and make allies and connections in order to get what they needed to defeat the British war machine. For the British it became far too expensive and protracted and the distance from home made it more of a problem.
As a previous post mentioned, there were times where the revolutionaries were willing to fight outside the accepted rules, hit and run, sniping, etc., tactics which the British felt were beneath them. This helped to draw the war out and gave the Americans small successes but enough to keep the hopes alive long enough to wear out the British will to fight.
- The British failed to increase their military numbers sufficiently to fully defeat the colonial troops.
- The British also failed to financially support their cause.
- The British failed in their attempts at winning the war in the South.
- The French entered the war, adding needed troops and warships (and financial aid).
- The colonial army had an outstanding leader in George Washington. Additionally, other outstanding commanders rose to the occasion, such as Nathaniel Greene.
- Hit-and-run tactics utilized by the Americans (i.e. Francis Marion) successfully prolonged the war.
- Support for independence continued to grow in the colonies, adding to moral, financial and troop support.
In my opinion, it was succesful because the British people and government did not care as much about the outcome as the Americans did. This is similar to what happened to us in Vietnam.
The British people and government were not willing to spend all this money and undergo any hardships to keep America as a colony. That is why they pretty much just gave up the fight after Yorktown. They could have kept fighting -- they still dominated the big cities and were pretty succesful militarily. Instead, they just figured that the chances of winning were too low to make it worth the cost.
The American Revolution was successful because the Continental Army had more to fight for. While the Redcoat's simply went through the motions. The American's were not trained militia but fighting for their independence. The American's had a better feel for the geography (home field advantage) and used this knowledge to make up for their lack of military training.