Using the comparison of "Canada" is no more accurate than using the comparison of "USA" as a whole. Both are roughly the same size land wise and both have areas that are better for whitetails than others are.
Like some states, there are parts of Canada that do not produce record book whitetails, in fact more areas do not than do. Sure you'll get the odd one from other areas but the majority of Canada's record book whitetails come from SK, AB, and MB, the latter having the fewest of the three. Even that could be misleading to some degree as the provinces are so big they could encompass multiple states and areas within them are more known for mule deer, or elk, or moose, or pronghorns, or bears, than they are for whitetails.
Liv is correct in saying that they true number one factor in reducing the number of record book deer up here is brutal winters. The severity of a winter is a good predictor in the number of record book animals that will be taken the next fall.
I did read somewhere that SK has the lowest number of hunters and deer taken per booner, not sure if it is true, but I do not doubt it at all.