edit - I found the source for the graph here but it doesn't seem to explain how they deal with jurisdictions with 0 SCs.
Those places are tied for last in the number of Superchargers, but they are also near the bottom in population as well, so they end up with scores near zero. Quebec stands out as #16 in the number of residents while still being 40th or worse in Superchargers.
The margin has generally been less on S and X sales in Canada than in the USA due to Tesla absorbing the 6% duty for not enough North American content. With the battery manufacturing shifted to Nevada, perhaps this duty will disappear and Tesla will devout more resources to the Canadian Supercharger network.