Not just that, nsa can observe enough of the whole intrnet traffic and do deep packet inspection.
Afaik tor does explicitly not protect against such an observer in their threat model.
Bitcoin does not require all that energy it actually protects itself by making it more difficult to mine when more energy is thrown at it. See difficulty adjustment.
But people will throw more energy at it in the future. There is no reason to put all unused energy into Bitcoin mining.
> The US government certainly has the budget and the power to be able to do a 51% attack and wipe out all faith in Bitcoin but they have no incentive to do it.