Uhm, have you even thought about the magnitude of such an operation?
You are exaggerating, the hash rate currently stands at less than 300 TH/s, and electricity and cooling are much less of an issue than they are with GPUs. Anyway, if a microscopic company like Avalon can sell 3 TH/s to another microscopic company in Switzerland for $300,000, I don't think it would be difficult for an agency of the U.S. government to spend several million dollars to manufacture and run 700 TH/s worth of miners.
I think Bitcoin will be vulnerable to a 51% attack for at least another year.