"pretty easy"? Exactly how do you Envision this attack going down, step by step?
Or they just deploy their own mining pool.
Or the just tax all of their citizens’ cryptos.
They have lots of options, since they have the power of the state behind them.
Soft and hard forks are a defensive mechanism against 51% attacks, essentially making them an always losing proposition outside of the immediate-term where the attack is occuring, because the attacker has to expend so much money, and then a simple code change could revert it, which would likely happen in consensus for the network if such a malicious attack would occur. Hence, no rational actor will likely even consider a 51% attack.