By the 1750's Great Britain had long established successful colonies in North America. A whole new generation was born in North American colonies as 'colonists' who understood that they belonged to Great Britain through lineage.
The language they spoke, the products they imported and most trade was conducted with Great Britain. Every year, government officials would visit the colonies and news and print were centric to Great Britain and it's 13 colonies.
However, the colonists also paid taxes to London. This seemed acceptable to earlier generations who had actually immigrated to the New World and still had connections with Great Britain. However, for the new generation of colonists, all they knew was their colonies and they did not have any particular affiliation with Great Britain.
As the colonies were so far away, they had started to build their own distinct identity. Their accent, way of life, music and their own folk stories were started to differ from those of Great Britain.
Things came to a difficult point when Great Britain would levy taxes on them. Since the colonies were directly controlled by the Crown and had no representation in London, this was seen as unfair.