I ask this because I was reading on the American Civil War, and the reasons why the Confederacy lost against the Union, such as the Norths higher population, more railways, better economic and industrial infrastructure, etc.
I apologize if this question sounds dumb, if it helps I'm Canadian and although we have a general sense of US history we aren't taught exactly the historical wars that lead to its independence.
They didn't allow it. They fought a war over it. French money, munitions, soldiers and naval forces proved essential to America's victory. The French goal was to weaken Britain, both to keep it from getting too powerful and to exact revenge for the defeat in the Seven Years' War.
War is very expensive and the people did not want to pay taxes. They still had other colonies like India, which could give them cotton and other raw materials.