They can't control cryptocurrencies but they can certainly create their own and ride the wave of interest cryptos have gathered over time. Seeing that people still drool over cryptocurrencies and how easily people can be swayed with only the term, they're willing to jump on-board and keep up with the decentralized cryptocurrencies in order to gain control towards people's spending. State-issued cryptocurrencies really aren't appealing, since it's like fiat but with more control over what you do and more eyes on what you use it to. It's very disturbing to know that every step of the way, someone sees what you do and what you use your money at, and to know that it's easily achievable through state-issued cryptos, it just becomes scarier.
If the central bankers (us government) prints dollars then to me they control crypto and Bitcoin. They can simply print money and buy. This crypto revolution would not be happening if they didn't want it to be happening. Look what they did to Libya, Iraq. Both of these countries leaders attempted to buy oil in something other than US Dollars. They got smoked. Now Syria, North Korea and Iran are in their sites. These people do not fuck around and kill at will to protect their money printing. The only reason we have crypto is because they want it.
I believe they will use the blockchain to track our every transaction much like we have video cameras on every street corner. it will be for our safety of course.