It isn't true that the US government could easily bypass the publishers. They want the research to be distributed, and peer reviewed, and have historically relied on the publishers to do that. The NIH (the federal agency that dispenses the bulk of academic funding in the US) took the view that they could get better distribution terms on behalf of the US public, with their open access mandate in 2008. It's this policy that the journal publishers are trying to reverse. Distribution, and peer review, are evolving, but they haven't evolved to the point where the US government could easily bypass the publishers.
I understand where you are coming from and I see your point. However, I'm not saying it would be "easy" just "relatively easy", as compared to the work and cost involved in legislation, investigation, and enforcement of the act which has been proposed.
Setting up a new system would not be without hurdles, of course, however if the initiative is properly funded and is pushed from the cabinet-level (i.e. US DOE) down and the use of the new system is tied to federal funding for universities, then it will gain traction and prestige.
It might take a generation for the old guard to fall away but eventually we'd have a better, more transparent, fairer system.
