We want to be what we want without you always saying no
Magan Carta took power from the king and protected peoples rights of trial by jury and due process.
The king had power to decide whether colonies existed and that angered the colonist and that let them to want to separate from the king.
Colonies formed a confederation because they all had a common purpose. They agreed to from a boycott(refused to buy British goods) and that led to the American Revolution and finished with the creation of The Declaration of Independence.