A 51% attack could be performed against #Bitcoin by any of the large State actors - China, Russia, USA. Per the article, even the inefficient ASICs would consume only as much power as a single large nuclear reactor.

Analysis: Bitcoin Costs $1.4 Billion to 51% Attack, Consumes as Much Electricity as Morocco | CryptoSlate

https://cryptoslate.com/analysis-bitcoin-costs-1-4-billion-to-51-attack-consumes-as-much-electricity-as-morocco/