What does it really mean to have each-other's backs?
I think one thing would be making some agreements in advance when it comes to refugees. Make it easier for Canadians to escape to the EU if the US does something stupid, and make it easier for Europeans to move to Canada if Russia does something crazy.
Other than that, I don't know what immediate steps could really be done. I'd love it if Canada would adopt some of the European privacy regulations, ditching the American-style laws currently in effect. But, a lot of things wouldn't be easy to change. Our cars, appliances, construction techniques, electricity voltages, plug designs, etc. are all very American-style, and those kinds of things have a lot of momentum.
But, I don't really see a downside to making the movement of people a little easier. I think plenty of Canadians would love to live and work in Europe. I think a fair number of Europeans would love to live and work in Canada -- at least once Canada finally adopts proper vacation lengths, parental leave laws, etc.