The '7 Years War' called the 'French and Indian War' in North America was a big 7 year war between the British and French colonial empires for which of the two would be top world power. In the War the French lost...big...By winning, the British empire became top naval power and top land power of the world. In North America with the big help of the colonial Americans (then fighting loyally on the British side) the British got all of formerly French Canada, and the land from the Appalachians to the Mississippi river, doubling the size of colonial America.
It changed relations because after the War ended (1763) the British wanted the colonial Americans to pay them back for the cost of the War in North America, and pay to upkeep and administer the won land to the Mississippi....while the British would keep for themselves control of that won land and of Canada and keep the American colonials out of both.