They were subjected to 170 years of mercantilism prior to the American Revolution. Any American ship that dared trade with any power other than the British Empire was deemed a "pirate" and was fired upon by cannon.
America did not exist. It was a settler colony of the British Empire. It was, if anything, the beneficiary of mercantilism, and not being allowed to trade with other nations is pretty much just how things were at the time.
