Don't economies of scale work in medicine? Also, isn't most of new drug research funded by private companies?
I'm betting that one of the main differences between Portugal and the US is the percentage of the GNP that's spent with the military. Proportionally, the US must spend a lot more of its tax income with the military.
http://en.wikipedia.org/wiki/Tax_rates_around_the_world
Edit: I left to start my dinner, an now it's too late.