They cannot take it down. Can you take down Internet ?
Yes , you can. The free internet project it's just a joke at the moment. The main traffic still relies on cables and satellites.
Take down a few cables like that grandma did in Georgia? (the country/not state) and problem solved.
Also the routing servers can be taken down easily.
I remember somebody saying that the us has 10 times the amount of rockets needed to destroy 90% of the largest databases in the world.
So , yes , it can be done. But nobody is insane enough to try it.
Also , why the internet , just raid the location where the mining pools are take control and ..1 hour , 10 blocks , bitcoin problem solved.
At the moment bitcoin is a grain of sand compared to other things the government is preoccupied.
Hopefully , until it becomes a real problem for them we will fix some of the vulnerabilities.