Those are good points. I think the first question is a bit skewed, as it is largely US companies using US consumers to subsidize research. These companies sell drugs much more cheaply in other countries, but they still sell at a profit vis-a-vis manufacturing and distributing costs or they would sell. When the US system goes socialist this foreign advantage may disappear, or the government may just as easily decide that we have a moral obligation to sell life-saving drugs to other countries for less money than we charge ourselves.
Also, please note that the inefficiencies you quote don't go away even with a single payer system. Someone still has to do all that paperwork or else there is massive fraud in the system; people can't just say "I'm a doctor and I saw a hundred patients today, you owe me X amount of money." These are the very tasks that government often contracts out to private firms because they can do them so much more efficiently.
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If the United States placed caps on drug costs like other countries, a great deal of the medical research currently performed would dry up. The U.S. market is essentially playing the same role as "early adopters" do in technology - willing to pay premium costs for the latest greatest and making the costs of research worthwhile. Once the research has been done and the drug being manufactured, the marginal costs to produce more units is almost nothing, so therefore there is no great loss in selling a few extra to other countries for lower rates than the U.S., so long as someone is paying the price premium for it.
If the U.S. adopted price controls as well though, the entire system would collapse. It's basically a Prisoners' Dilemma situation - a country could gain an advantage by imposing drug price controls, but if they all do then none will get a benefit and indeed be worse off.
If no country or market is willing to play the role of "early adopter", then there is no point for the drug company to produce a drug that won't recover their costs since price-controlled markets essentially turn a new drug into a commodity priced good. It's only in a non-price controlled market that companies will bother to engage in R&D - why would you spend billions to produce a drug if universal price controls meant you couldn't recover your costs and make a profit?
So go ahead and advocate for price controls in the U.S. but just be aware that you are essentially trading any hope of new miracle drugs in the future for getting cheaper today the drugs of the past.