The fact that they've got us discussing this issue in terms of importing drugs from Canada means that they have succeeded in obscuring the issue.
The Canadian health system is able to get significantly cheaper drug prices, while still respecting patent protection, by using access to the demand for drugs generated by the over 30 million beneficiaries of its system. The drug company agrees to charge less, still enough to make a profit, but less than highway robbery, because if it doesn't, it doesn't get to sell to the system at any price, and therefore not make any profit margin from selling to over 30 million people. This is all free market. Canada can't and doesn't make Big Pharma pay less by legislative fiat, its health system simply uses the market power of access to 30+ million patients to dun down prices.
The US govt directly, by way of Medicare and Medicaid and the VA and military medicine and many other programs which provide medical care or insurance, controls access to way over Canada's 30+ million. Many US private insurers control access to over 30+ million. Why do none of the above use their market power to do what Canada does, and dun down drug prices?
In the case of the US govt, the answer is straightforward. It is forbidden by US law from dunning down drug prices. Why would the US pass such a law? It's the Golden Rule of US Politics, "He who has the gold makes the rules.", and Big Pharma has some big gold to throw around.
But what keeps the private insurers from using their market power to get lower prices for drugs? Drugs are a hefty component of their total costs. If they reduced what they have to pay for drugs significantly, it would give them a significant edge over the competition, and allow them to keep some of the difference as pure profit. We do have a free market in health care and health care insurance do we not? These corporations are competing ruthlessly, red in tooth and claw, for survival of the fittest, are they not?
Well, not exactly. There's the Pogo Rule of US Business, "We have met the enemy, and he is us.". There's no percentage in dunning down what a fellow member of the cartel charges you.
One way or the other, however the trick is managed, this issue makes clear that we have an effective cartel in medical care and medical insurance in the US, a cartel fostered and protected by govt action. Don't help the cartel obscure that by talking about this as if Canada has anything to do with it.