The US has some of the lowest cost generics in developed nations - prices tend to be lower than the EU. The US has some of the highest generic drug penetration of developed nations. [1] That's because of things like the 180 generic drug exclusivity and mandatory generic substitution laws.
The 180 exclusivity is a big part of that. If you open the flood gates to any generic manufacturer, the margins disappear so quickly that some manufacturers won't even bother to try. By dangling a massive carrot whereby the generic manufacturers can quickly recoup costs and make a large profit, it drives generic companies to compete to the enter the market.
When Lipitor went off patent, eleven generic companies entered the market and prices dropped 95%.
The US generic market is one of the best functioning in the world.
https://www.fda.gov/drugs/abbreviated-new-drug-application-a...