According to the Canadian government, Canada has only been the leading oil exporter to the US since 2004 (17% of petrol imports and 10% of US consumption in 2004). As a "geographic region," the Persian Gulf supplies more oil (19.8% in 2004). But OPEC members supply the lion's share (40% in 2004). OPEC includes Venezuela and Indonesia, which are outside the Persian Gulf. Of all the oil suppliers, Canada is the most dependent on the US market.

Relations between the two countries have been chilly of late for several reasons: Canada declined to participate in Bush's fantasy missle shield program; Canada did not send troops to Iraq; US tariffs on Canadian lumber hurt their industry; and the ban on Canadian beef imports due to a mad cow disease scare haven't helped matters either. The previous Prime Minister, Paul Martin, was making moves to break Canada's dependency on the US oil market by seeking to supply China. His party lost the recent elections, but the new guy from the Conservative Party probably won't last long.

Canada is a major player in the US economy. But as to why they are treated like Rodney Dangerfield I don't know. Also, there's something fishy about the numbers in the Congressional Research Service Report linked above. CRS shows Great Britain is #1 investor in the US and Japan is #2. But in February 2002, the Washington Post estimated the Saudis had between 500 - 700 billion invested in the US. I believe Michael Moore also addressed this in Fahrenheit 9/11. If true, that's more than Britain, Japan and Germany (the purported top three) combined.

Sorry for the messy appearance of the above. I couldn't get the formatting to work.