The Americans were tired of all of the things that the British were doing to them. First of all, they were taxing the Americans, since they were still poor from the French & Indian War (which happened in North America, which is why England thought the Americans should pay for taxes). The colonists were also mad because they were making these taxes even though they were not getting any representation in Parliament.
The Boston Massacre also angered colonists because the soldiers shot "innocent" colonists (even though they were throwing rocks and snowballs with rocks in them).
After the Tea Act was passed, the Sons of Liberty planned and did the Boston Tea Party (which you should know), which angered England. They passed the Intolerable Acts, which closed down Boston Harbor (which was very important to Massachusetts making money). And part of it was the Quartering Act, which cause British soldiers to live with the colonists. And when they were on their break, they wanted to find jobs (because the had little pay) and would try to take the colonists jobs, which (obviously) angered the colonists.
The introduction of the horse to the plains Indians had a dramatic effect on Indian culture. Indians quickly adapted to using horses for warfare and hunting. Indians relied on the buffalo to survive. With the horse, they improved their ability to hunt to the point that they were able to create a surplus.
