Algerian, Nigerian, Angolan and Libyan are having trouble in this market because they are mostly ultra light grades(API Gravity 38-42) and have lower Distillate yields. Overall, Canada's crude slate is heavier with better Distllate yield but going to the U.S. with too much of its production will be problematic.

http://news.yahoo.com/analysis-once-prized-african-oil-struggles-markets-160330679.html