I don't know in what world your idea would work. Why should U.S. companies sell any drugs to other countries if they didn't make a profit? Why should I subside sales in one country with the profits from another country other than trying to increase market share to later raise the prices? If a local branch does not manage to gain the margin I expect, I just close shop there.
Ironically, in every country I have heard the same complaint. There is a rumor that a drug is more expensive in your own country than in another one. That's always a clear proof that you pay the development of the drugs sold so cheap in the other country. I've heard the same in Germany, in France, in Spain... As it seems, each country pays the development of a drug for all the other countries in the world.
No. The reality is that each company charges the maximum for a product it can get away with. If the conditions in the U.S. allow to charge on average three times the prices than in other countries, then why would a company not do so? Why should it voluntarily forfeit two thirds of revenue? It has nothing to do with Research & Development, but all with trying to maximize profits.