Well, the reality would be more like:
If Canada joined the US, it would do so as 11 states. The Inuit Territory in the Arctic would have to be resolved as either a state or as a new reservation as it has sort of that status in Canada now.
As for the 11 or 12 states, approximately a total of 45 Representatives would fill seats, but unless Congress changes the 1929 law on how many seats in the House--good luck with that--what would happen is an approximately 10% reduction in the number of seats apportioned to states with more than one Representative would occur. That means major states like California and New York would lose about 6 and 3 respectively, maybe more.
Given that most of Canada is not all that liberal / Leftist, most of the new states would end up in the Republican corner. Worse, since the US has the two-party system, the parliamentary system Canada uses end and again, the Left loses in that outcome. The province of Quebec would no doubt throw a major fit over French no longer being allowed to dominate across what was Canada.
Now, if the Inuit territory became a state too, it might cause problems with Native Americans as well as with the Inuit who find their status under Canadian laws no longer applies. If instead, it became several reservations (there are different tribes involved) it would have very limited political clout compared to what it had under Canadian law.