The loss of the American colonies
Most of the east coast of North America was British in 1750. From the farmers and fishermen in the north to the tobacco-growers in the south, they all flew the British flag and obeyed British laws.
Canada was French, and the French were often at war with Britain. In some parts of the British colonies, the men always had to be ready to defend their homes. So they were glad to have British troops on their side. And they paid taxes to help pay for the troops.
In 1763, after victory in war, Britain took Canada from France. So the threat to the colonies was gone. But the taxes remained. And it was Parliament in London that fixed the taxes and made the laws.
The laws on trade said that Americans must buy imports (e.g. tea) from British merchants. And they said that exports (e.g. tobacco) must be sold to British merchants. In the colonies, they said that this was unfair. They said that they should fix their own taxes, and make their own laws.
The quarrel turned to war in 1775. The American 'rebels' formed an army and chose George Washington as their leader. At first the army was badly armed and clothed. It nearly lost the war. Then the French sent help, and the tide began to turn. In 1781 the British army at Yorktown had to surrender to the French and the 'rebels'.
Peace was made in 1783. The colonies got their freedom, and joined together to form the United States of America. Britain kept Canada, though, and some loyal subjects moved there from the new U.S.A.
Walter Robson: Britain 1750 – 1900; Oxford University Press, 1993/2002, page 12