With the drop in oil prices from the past years, getting oil out of the ground in the US became too expensive. A lot of newly installed sites were closed because they could only operate efficiently with an oil price near $80 a barrel. I am quite sure the US imports a lot of oil...

Edit: quick results from 2015: 25% is imported. https://www.eia.gov/tools/faqs/faq.cfm?id=32&t=6