What about poor countries? If a drug company had to sell drugs for the same price in the US and a country like Sudan, the result would almost certainly be raising the price in Sudan up to US prices rather than lowering the price in the US to Sudan prices.
That would put the drug out of reach of most of the people in those poor countries.
I mean, I don't think you're enforcing patent law in South Sudan regardless, but they're also just not capable of manufacturing such drugs. To get a trustworthy drug, they pretty much have to buy it from the patent-holder. India, China, and maybe Brazil are about the only exceptions. Theoretically, I guess you could say we just expect the third-world to rely on black market medicine from India, but uh, that has some risks involved.
They can do what India and some other countries do, and legislatively ignore pharmaceutical patents when it comes to public health if drug is deemed unaffordable.