Which govt... ( there are more than one and they tend not to get along too well most times. )
And how do you turn off something that doesn't have an "off" switch? Bitcoin doesn't even require "the internet".
First world govt's. You dont "turn it off" you make it illegal. It wont stop completely obviously but no real business will touch it ever if its illegal. Most people will also stop using bitcoin if it becomes illegal. Bitcoin does require the internet. How do you think coins originate?
I always get a chuckle when I hear people talk about making bitcoin illegal. What part could they outlaw? ECDSA?
IF bitcoin "took over" how do you think the govt would fund road repairs and every govt expenditure etc etc? I mean be realistic. You honestly think a deregulated currecny woudl be good in the long run??? I dont think the federal reserve is any good but you need regulation and law enforcement.
Probably with taxes.