Part of that is specifically that other first world nations have regulations to prevent monopolies in place, like mentioned. For instance, Canada's patenting on medicine allows generic brands to come out after specified time, thus increasing competition and causing their medicine to be significantly cheaper. If the inventory is gauging people with prices, eventually another company can come in and make the generic one cheap for everyone. In America a pharmaceutical company can have a patent on a life saving drug preventing anyone else from making it, and the ones responsible for paying for it are healthcare insurance. A Canadian pharmaceutical company may be inclined to drop their pill price to cheap so healthcare companies continue to work with them even when the generic becomes available. In America the Pharm company could charge healthcare $1,000 a pill, with no relief in sight, and all the stress in the world on the healthcare system, no fear of competition.
We have other regulations and things in play in America that affect our healthcare system, and it does indeed involve monopolies.