Do you think they could have a branch on government to do something about crypto or is it like too small to care? I mean they have bunch of branches for everything, having one for crypto could be different and with all the tax they could get from tracking every single person and asking for tax could mean that it would be a government branch that actually profits as well and not cost money. If they do something like that, it could both manipulate bitcoin but also it could help you out as well.
So, would you prefer something that allows governments to manipulate bitcoin but can't control it (decentralized currency after all) but that would help you too, or would you want government to be out of it all together even if that means it would hurt you? I am not entirely sure but the reason why bitcoin was created was a bit of resistance towards current system so I would say latter would be better.
Well, the only method I can think of to actually make any sort of manipulation that they could even make a profit from is actually that doesn't require moves with money to manipulate, sure they need money for the profit part but the manipulation doesn't require any money at all.
If you are a big nation, just tell the world that you are considering banning bitcoin all together, and even have a public announcement that you want to meet other big world leaders on potentially banning or at least limiting very much with full government knowledge (like KYC but harsher) to even own bitcoins, that will drop the price a lot. Buy as many bitcoins as you can as government when the price is that low and continue to be harsh.
After a while when you have enough, tell everyone you changed your minds and you will allow bitcoiners to exist and also will support them, that will increase the price a lot. You can sell after this stage.