The colonies became strong by keeping strict control over its trade that's how the belief in mercantilsim affect the colonies.
According to mercantilism, the colonies were required to engage in two general behaviors: (1) The colonies were locked into exclusive trade between the colonies and the metropole and were not allowed to trade with any other nation or colony. (2) No manufactures or complex goods could be made in the colonial territory. As a result the colonies would provide wealth to the metropole by trading their natural resources for less than they would be worth and by buying manufactures for much more money.