Having lived in both countries, I’m not sure there is that much of a difference. Pretty much all the large US cities have public transport. The only Canadian cities I’ve seen with something close to say NYC are Toronto and Montreal. Getting around mom Skytrain in Vancouver is doable, but painful from a lot of areas.

And of course Canada has one of the lowest population densities when you average the population across the swaths of uninhabited arctic. But 90% of Canadians live within 100 miles of the US border in a handful of cities.