One other thought, I think if the US Government truly did believe BTC was unstoppable, they would just try and co-opt it. When BTC was first “introduced,” one of the selling points was that it offered complete anonymity, and then come to find out it actually offers none. Perhaps this was propaganda put out there to dissuade people from adopting it in the first place, by claiming only criminals used it. As long as there’s a central bank, there will probably not be a viable alternative currency. There will be speculation though.