The situation is more akin to the rapid urbanization in the third world. Infrastructure cant keep up. Just try GTA traffic. People move to Barrie just to afford a house in the GTA (Barries not GTA!).
Sure Canada is "empty", but its also an inhospitable frozen waste land with 90% of the population living within 100 km of the US border. When we say Canada is "full" what we mean is that Canada cannot build fast enough. That the 3000 km^2 worth living in in Canada are really really dense.