The stamp act was a tax, not a restriction, right? Britain was attempting to recoup losses from the French-Indian War if I'm not mistaken. And the colonists had no say in it and then realized that even after lobbying for years to remove it (hell, the U.S. sent Benjamin Franklin, the best statesman in history and even he couldn't get them to budge), that they would always be subservient to the Crown. The tea imports was just salt on the wound.