In general, the colonies were independent from Great Britain before they declared independence for several reasons. First, by the latter part of the eighteenth century, the American colonies were filled with people who had never been to England and felt no ties to the mother country. They had been born...
In general, the colonies were independent from Great Britain before they declared independence for several reasons. First, by the latter part of the eighteenth century, the American colonies were filled with people who had never been to England and felt no ties to the mother country. They had been born in North America, as had their parents, grandparents, and in many cases, great-grandparents. Others came from other European countries, such as Germany, and had never felt any tie to Britain. It thus became increasingly difficult for the British to assert authority over people who saw themselves entirely within an American context.
Second, the British had long let the Americans largely run their own affairs through a policy called "salutary neglect." This meant the British turned a blind eye to all the ways the Americans were violating British laws, such as prohibitions on trade with other countries. As long as the wealth was rolling into Britain from the colonies, the British were not inclined to interfere with Americans' "side business." Because of this, the colonists became accustomed to running their own affairs without interference.
The tipping point was the French and Indian War. The colonists were dependent on Britain's military might before that war: the French military was on their borders and entering into alliances with Native American tribes, which meant that the British settlers had to fear France attacking and taking over their territories. When Britain defeated France in the French and Indian War, so that the French withdrew, that threat disappeared. Suddenly, the Americans no longer needed the British. Increasingly, Britain seemed like a millstone around the colonists' necks, not a help to them.
Britain created a perfect storm when it wanted the colonists, who no longer needed them, to help pay for the costly French and Indian war. This was not an unreasonable demand, as the war had primarily benefitted the Americans, but it was not a cost the colonists wanted to bear. Having been used to running their own affairs, the colonists then resented the British suddenly interfering to try to raise extra revenues. In declaring independence, the colonists were simply stating what had in many ways become obvious: the two regions had grown too far apart to remain one nation any longer.