Even at the 'Changing of The Guard' ceremony in London, they played 'The Star Spangled Banner', in memory of 9/11.
EVERY NHL game in Canada, even where a US team was not playing, played 'The Star Spangled Banner' ahead of 'O, Canada!' and had two minutes of silence.
CAF (now called what they should have been call, RCAF) aircraft flew CAP over several US cities, in the days following the attack, to relieve US aircraft and crews.
Two hundred fifty-five US bound flights were re-directed to Canadian airports. Gander, NFLD, a town of about 10,000, hosted 6,600 stranded passengers and crew from 53 aircraft.
There were PLENTY of tributes around the world, in respect of 9/11.
Even PM Chretien covertly sent members of JTF2 into Afghanistan, to work with US SpecOps and the Northern Alliance. The Brits also sent members of the SAS and SBS to assist. All of this in September and early October 2001, before regular ground troops arrived.
Here are pictures of Gander and Halifax airports, when flights were suspended 09/11/01: 
On a personal level, I saw the second plane hit the Tower, as I was watching TV while getting ready for work. As soon as I got to work, I made an appointment the Red Cross to donate blood. The reporters suggested 15-20,000 injuries, so I thought so many casualties will require blood from blood banks all over Eastern North America. Calgary's Red Cross would have to ship blood East, to cover transfers from Ottawa, Toronto and Montreal to NYC. Luckily, there weren't 20,000 casualties; unfortunately, there were over 3,000 deaths!
A LOT of people all over the world did a LOT of things to honour the memory of the 911 victims, even if you don't remember.