I don't know how the pharma industry decides what to pursue, but it is at least plausible that part of the incentive for what they do depends on being able to price discriminate in sales to other countries. Before suggesting we tear down Chesterton's fence, it seems reasonable that you should have more justification than just that it seems fair to you.
I don't understand your concern -- how does proportional ownership eliminate pharma's ability to price discriminate? I just think the US government should receive some prorated portion of profits from drugs they subsidized development of, which can be reinvested into further development.
These are separate issues. You said that the US is subsidizing drug development for other countries and suggested that you would prefer that we didn't. That affects drug development incentives.
You're also saying that the US government should have some of the profits that the drug companies currently have. Presumably this would affect something that drug companies do. Shouldn't you be concerned that the thing it will affect is them developing new drugs?
Maybe the current situation isn't optimal but there's no reason to think that your suggestions would improve things.
