The causes of conflict are that Britain was attacking American economy. Such as Boston Tea Party, The British monopoly North America tea import, and controlling prices, etc. In colonies of Britain, because of the mode of British government used so that almost every colonies had freedom and thought of democratic consciousness. The people who live in the northern America colony for twenty to thirty years had deep effects of it. Even the young people who were born in colony in new generation had more a sense of belonging and national identity on north colony than their actually homeland which is Britain.
Accordingly, Britain loses the hearts of people, but they were trying to caught back in the wrong way. Although, it looks peaceful in the inside of America, the wars from Europe that are separated by Pacific and Atlantic are still continually affecting the northern colony in America. On the military and policy sides, although the British military are the best, but the crossing- ocean distance between Britain and American truly reduce the military power. So it didn’t be helpful on supporting the British military.
At the meantime, Washington organized powerful troops and made a system for collectively resist British troops. Also, there are some countries, such as Netherlands and French which had enmity with Britain were supporting American being independent. Especially when America made public Declaration of Independence, French establishes diplomatic relations with America. French gave the American military supplies, food, and qualified military instructors to improve the combat effectiveness of the armed forces in North America. These elements did surely help American out on wining revolution.