The US is technically energy independent thanks to shale oil but, unless my knowledge is out of date, the shale business is only dabbled in by the big oil companies that own the vast majority of the big refineries in the US. Shale oil is dominated by smaller more numerous companies, it can scale up and down lightning fast by oil extraction standards, and it needs much less refining than most other sources of oil so the big oil companies import oil from all over to employ the refineries and due to their international entanglements. So there is the strange import export dynamic because there are two camps with broadly different incentives and a really complicated market.