The PM needs to be better briefed.  The USA has much light oil, Canada has much heavy oil.  US Refineries can actually make more money by processing heavy sour crude.  Refineries in the Gulf Coast and US Midwest have been modified into high-conversion facilities that crack  the heavy crude fractions into high-value products. These  facilities are specifically designed to process heavy sour feedstock, such as WCS.   

Refining margins (the 'crack' spread)  are better often with lower cost heavy crude feedstock than high cost lighter oil. That's why the demand for heavy crude is  high in the US and also becoming increasingly popular in Asian refining hubs. Further, US heavy oil from California is running low. The future of heavy oil is not dimming. Not yet.

The PM should have known this. However he was briefed by Butts who fed him the usual propaganda you'd expect from any anti-oil ideologue.  That's why he misspoke. OK, things happen. Let's move on, preferably with competent PMO staff.