I recently wrote something about this case in another thread.

First, yes, such an attack is of course possible. Besides of the high cost even for states, there is however also another problem. If the state-level agent wants really to harm Bitcoin, he would need additional measures which would make the attack even more expensive:

First, he should be able to maintain the attack for some time (was already mentioned). But second, to really initiate a big dump, he should create real damage, e.g. double spending several big amounts on big exchanges or payment processors.

For this to happen, he'd need to create a network of fake accounts on several exchanges, bypassing KYC measures. Of course he has to take into account that these exchanges have some safety measures in place, such as requiring confirmations for BTC deposits. It is likely that the attack would be noticed already in the timeframe between the 51% incited re-org and the moment the deposit gets "credited", or at most the intent to cash out by the attacker, and the exchange would simply refuse to credit BTC deposits which were the result of a double spend.

Atomic swap and no-KYC exchange liquidity should be too low to create such an "real damage" attack.

The state-level attacker could of course get, in theory, some of his costs back if he manages to short Bitcoins just before the attack. But shorting currently is only possible on centralized platforms. If these detected anomalies like a considerable number of shorts just before the attack, they would for sure initiate investigations. And the state-level agent would then be responsible for any damage created to nationals of other countries by the "short selling" part of the attack, because "insider trading" is a crime in all countries I'm aware of. So no, the most likely outcome is that he would get next to no "returns" from the attack.

What they could try is to inflict damage with the "cheapest possible" 51% attack, i.e. with only a small amount of double spends. But the harm created would then also be quite low. Several coins which were attacked in the past, like ETC, have since then recovered.

I think thus for state-level agents the "FUD attack" is much more promising: tighten regulations, trying to create narratives like "Bitcoin is harmful for the environment", or outright ban Bitcoin, the latter being probably possible only in authoritarian countries.