From your link

In the 2003 invasion of Iraq, the only fighting forces are from the United States, Britain, Australia, and Poland. Ten other countries are known to have offered small numbers of noncombat forces, mostly either medical teams and specialists in decontamination, making a comparable alliance of about 13 countries. The United States is expected to be responsible for essentially the entire cost of the war, at least $75 billion.

Combat troops:
United States - hundreds of thousands of troops, weaponry, money, etc.
Britain - 45,000 troops, aircraft, tanks
Australia - about 2,000 personnel: a squadron of F/A-18 Hornet fighter jets, three ships, 150 special forces troops, and other weaponry. See Australian contribution to the 2003 Gulf War.
Denmark - submarine & warship, and a medical team
Poland - 54 combat troops, 74-member chemical decontamination team, supply ship with 56 sailors; total troops - up to 200

In short, the US is paying essentially 100% of the costs. US troops made up about 85% of the personnel, Britain about 15%, Australia less than 1% and the rest essentially nil.

And maybe Canada hasn't spent bundles of $$ on the military because of a philosophy that there are other, better means to attain peace. But it's not like Canada hasn't contributed in the past.. with a population of about 1/10 that of the US, in WWII Canada lost 37,500 soldiers as compared to the US 292,000. Canada also contributed significantly to GW1.

And another and... "I'm sure nobody's bothered Canada because they are so nice and harmless, not because they've been squatting comfortably under the shelter of America's nuclear umbrella. " Who has been "bothering" the US lately? Islamic terrororists who, as I understand the right-view, hate the US because it is free and democratic and has western values and is "decadent". In these regards, Canada is almost exactly the same as the US, but nobody is flying jets into Canadian buildings.