What if, for example - like after that twitter hack - the President wakes up (in a bad mood) and decides with an executive order to make all crypto illegal in the USA?

Of course this probably will never happen in today's world, as the there is big money is invested into crypto currencies; but do you ever think that it is even remotely possible...

Or the next elected president is so "old school" and decides that crypto needs to go?

I don't mean only America, what about in your country; do think that a future ban on crypto currencies is ever possible in your country?