They are there because Article 5 of the NATO Charter was invoked for the first time in its history. More soldiers from the UK [152] have died in Afghanistan than Canada [116]. The US has lost 677.
Canada didn't not help us in Iraq.
Comparisons of the Butcher's Bill are invidious.
But as you have chosen to do so, bear in mind that Canada has half the population of Great Britain and one tenth the population of the US, so we are paying a Butcher's bBill disproportionate to our population.
The World Trade Center was attacked on September 9, 2001. Immediately following that attack, and before Canada was asked to do so, Canada uilaterally and without being asked, detached naval assets from NATO and sent them to the Gulf to work with US naval forces. This was before the Brits deployed naval assets.
By December 2001, Canadian JTF2 (special forces) bricks were in Afghanistan. By February 2002 Canadian regular forces were in Afghanistan.
Two of the hottest provinces in Afghanistan are Helmand where the Brits are deployed and Kandahar where the Canadians are.
Rumsfield wanted Canada in Afghanistan to enable him to deplloy additional forces to Iraq. We were already there and he felt that we would be best used there.
Notwithstanding posturing by our then Liberal prime minister, Canadian officers attached to US units were left in place even when the units were sent to Iraq. This included line officers in charge of line combat forces while drawing Canadian pay and allowances.
As for NATO obligations regarding the 9-11 attacks, I could never figure out why ALL of NATO was not immediately mobilized to invade Afghanistan. It was a clear attack on a member nation which, by charter, had to be answered by EVERY member nation.
NATO started to die with the Serbian war, where it attacked a nation that was not even threatening a NATO member. It expired on 9-11.