Of the refineries I deal with, they process a combination of Russian, Venezuelan, Canadian and Eagle Ford (local to south-central Texas) crudes. Most gulf coast refineries (which equates to the vast majority of our country's refining capacity) are designed and optimized for very heavy (read not American) crudes. All politics aside, a pipeline from Canada to Houston would have been ideal for safe transport of crude oil. As for now, Canadian crudes are shipped via rail to Mexico then barged into the Gulf coast refineries.
It is true that a lot of finished product is sent overseas, but that is mostly Diesel. Cost of refining to make Diesel/Kerosene vs Gasoline (or premium/alkylate) depends in the refinery's design, the crude slate and how the processes are optimized. Down here, Diesel proves to be more profitable...especially the superior Diesel that European countries require. Therefore, refiners balance what they make to optimize cash flow and increase the value of their stock shares.
The refineries in Leroy's area likely process local (Pennsylvania/New York) shale oil along with heavy Candian oil for a lighter blend. I have stayed out of the processing business of Delaware City and Paulsboro refineries for a couple of years now, so this is just speculation based on their design.