Step-by-step explanation:
Because the British were in debt (7 years wroth of debt) after the 7 year long war. Even though the British won, the British were left with a war debt which needed to be payed back, so they decided to heavily tax the colonists (the people in the 13 colonies).
Since the colonist were "poor" they almost couldn't afford the high taxes so they were left homeless (some of them), so that caused the colonist to be upset!
(sry if wrong!)