ok, but ...
the US consumes about 20.7 million barrels per day (bbl/d) and imports 1.61 million bbl/d of that from Canada - about 8%. domestically, it produces about 7.6 million bbl/d (but actually exports about 1.0 bbl/d of that). in total, the US imports about 13.1 million bbl/d, including: 1.55 million bbl/d from Mexico; 1.45 million bbl/d from Saudi Arabia; 1.25 million bbl/d from Venezuela, and; 1.07 million bbl/d from Nigeria. (all 2005 data, things have changed, Im sure)
while Canada may be the single largest exporter to the US, our proportion is only 21% of what the US itself produces domestically; only around 12% of its total imports, and only 8% of US total consumption. so, the title "Biggest Oil Supplier" is a tad misleading.
the bigger deal, i would suggest, is natural gas. virtually all US imports come from Canada, and make up for almost 20% of total consumption (compared to only about 8% for oil).
amazing what the CIA will tell ya