In 1776, Britain had 13 American colonies. Actually, Britain had more colonies than that.
It had 14 mainland colonies: the angry 13 plus Canada. It also had several Caribbean colonies. About 2 million colonists lived along the Atlantic coast. If you had traveled through these colonies in the early 1770s, you would have had a hard time finding people who called themselves Americans. Most colonists thought of themselves as Virginians or Pennsylvanians or New Yorkers. That began to change as the colonists became unhappier with Britain. As they united to fight their ruler, the colonists put aside their differences. They started to think of themselves as Americans.