Because the country was essentially thirteen colonies fighting separately, the British had to deal with battles throughout the country, with people who were fighting for their homes and towns. The American forces knew their surroundings better, and they were motivated to fight well to protect their loved ones and neighbors. The Declaration of Independence, written in July 1776, indicates how resolved most of the population was to independence from Great Britain. Thomas Jefferson, author of the document, wrote that the British government had become "destructive," and people believed they must assert their independence and be free of the country, or their lives would never be free from oppression. He wrote, "That whenever any Form of Government becomes destructive of these ends, it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness" (Jefferson). Essentially, the people declared their freedom before they won the war, letting Britain know that even if they lost, they would never put up with tyranny again. The document shows the mood of the people, it shows how motivated they were to be free, and that is another reason they were victorious. They had more to lose than the British did, and they were fighting on their own ground, for something that was incredibly important to them, and so, they were far more motivated than the British soldiers were.

Justifications

The colonists were justified in wanting their freedom from Great Britain, because Great Britain was demanding too much and providing too little for the colonists. The colonists won the war because they were more devoted to their cause, and they had more to lose. Many were also interested in creating a new form of government, where the people were represented rather than ordered about, and they began to develop the documents that shared that vision. The Declaration of Independence gave a voice to their concerns and beliefs, and most people (but not all, of course), supported those beliefs. The Constitution also helped frame those ideals and that vision of a republic that was "by and for the people." Another group of writers note, "Short of rebellion, a constitution was the only mechanism they believed capable of exerting that vital restraint. For the Revolutionary generation,...

These documents said the people were serious, they meant business, and they would not be satisfied until they were free. They were fighting for ideals and principles, and those things can be extremely motivational, especially when they have been withheld in the past.
The Americans did not win because they were stronger, or better equipped. They won because they wanted it, but there was another important factor to their victory, and that was the French support. The French brought another layer of fighting to the war, but they brought much-needed supplies and equipment too. They were there at the final Battle of Yorktown when Britain surrendered, and they were there at other major battles, too. The French support really was crucial to winning the war, and its importance cannot be overlooked in American history.

In conclusion, Americans fought for their independence because they wanted to be free from tyranny and oppression. They had initially come to this country because of religious oppression, and they carried these ideals with them throughout the country's history. They wanted to be represented in the British government, and they wanted a say in their own government and economic processes. They did not want to be taxed unfairly, and they wanted to make their own political and economic policies. They won the war because they were more motivated to win, and France leant vital support that kept supplies coming. They also won because they were fighting on the own turf, while the British were fighting far away from home on unfamiliar ground. It was a time of great change for the country and the people, but they desperately wanted change, and that helped propel them over the British to gain their freedom.