The opportune time to squash Bitcoin was back in 2009, and even in 2011 - but now the network is really gaining traction, so I think that ship has sailed.
Politically? Yes. Those fools on the hill will
NEVER catch up to the tech.
But technologically? If there is a will to do so someplace like at Bernanke's office? Sadly, no. He could print a quick trillion to build a 3rd-gen ASIC factory and make enough chips to sustain a fatal attack on the network... All without telling congress anything.
If bitcoin falls, that's how it necessarily went down.
...At least we'll all know what happened though... We'll see it in the network hashrate graph. If the world loves bitcoin enough, we'll simply crucify his ass, torch the fed to the ground, and start over.