Unfortunately, this commonly-cited argument is propaganda. And pernicious: it appeals to nationalism, framing US citizens as noble suckers who somehow help the entire world by letting corporations rob them blind. (With scare-words like socialism, framing it in terms of economic patriotism. Evil countries unleashing efficient socialist negotiators against poor capitalist Big Pharma.)

Public Citizen and many others have done research debunking such claims in detail. (http://www.nybooks.com/articles/archives/2004/jul/15/the-tru...)