The American Revolution occurred, because the colonists were tired of being mistreated, with heavy taxes imposed on them, having to quarter unneeded troops in their own houses, and not having as much freedom, that they decided that it was best to break away from the British Empire The Massacre at Boston proved to be one of the last straws.
There were multiple reasons. (Taxes, The Boston massacre, Customs Racketeering) Basically the Americans were sick and tired of British enforcing things on them when they had no say in what was happening to them.
