“Because American refineries require specific crude blends (and to maximize global market efficiency), the U.S. exports a significant amount of its crude and refined products, while concurrently importing crude oil.”

The US exports a majority of its oil as they don’t have the refining capacity for the type of oil (light sweet crude) it produces. They import heavy crude (mainly from Canada) that they use for domestic use as refineries are designed to refine heavy crude, and US heavy crude production has nearly run dry, mainly from California.