The branch plant mentality, and the resource give away. It's a big US company in Canada reaping the benefits (but only 1/10 of what they reap in the USA.) And yes sometimes, it's a big (as in big for Canada) Canadian company in the USA reaping (ten times) the benefit but that's rare.
Canada's 100 biggest companies by revenue in 2012...
http://www.theglobeandmail.com/report-on-business/rob-magazi...
22 BCE Inc.(De11) 19,588,000 7.69
20 Bombardier Inc.(De11)1 18,882,000 11.99
26 Research In Motion(Ma12)1 18,456,000 -7.33
27 Bombardier Aerospace(De11)1 18,347,000 -1.14
29 Bell Canada(De11) 17,133,000 9.34
53 Telus Communications(De11) 10,397,000 8.4
54 Telus Corp.(De11) 10,397,000 6.27
64 IBM Canada(De11) 9,051,000 14.3
Having only 35 million people spread across one of the largest countries in the world makes it difficult to spawn consumer and retail conglomerates. Nintendo and Sony excelled in part because Japan was a perfect playground for testing personal technologies. Walmart had 300 million customers, 90% of which live in extremely developed locations, which allowed for retail stores to spread quickly and profitably across the states.
Further, having a history of less than 50 years means that less sustained activity has likely been driven from within Canada as opposed to from overseas. Given the choice of where to locate, a tycoon from Toronto had the choice of working out of London.