The governments can't control Bitcoin because it is decentralized. It wasn't made in favour of a centralized system where one person or authority can have full power and control over its transaction. The farthest the governments can go is to impose regulations on Bitcoin transactions especially on the exchange sites.
Obviously, Bitcoin is a decentralized platform so you think government can't control the Bitcoin.
Seems like that from it's own intention to exist, bitcoin was decentralized.
But reality government can add some regulations of Bitcoin because each country have different set of regulations in government policy so they can add some regulations on convenient manner.
It's the power of the government, if they see that there's a need of implementing rules then law will be there to accompany the ruling.
The current situation many exchanges ask the proof of the country so government will monitor our activity.
Government seek for any illegalities as there are chances that money laundering and illegal transactions can happen using bitcoin.