In the late 1700s, Thomas Jefferson wanted the United States to adopt a unified system of measurement and saw the metric system as the best solution. However, a pirate attack in the Caribbean disrupted these plans. Joseph Dombey, a French scientist carrying a kilogram and meter stick to demonstrate the metric system, was captured by pirates. By the time France sent another scientist to explain the system to the Americans, Jefferson was no longer in office, and plans to go metric were disregarded.
Strictly speaking, there are a few places where Imperial measurements diverge from US customary measurements; the sizes of a fluid ounce, pint and gallon are a few examples.