No I do not think that banks can be destroyed by the bitcoin itself, the government will indeed stop this and the banks itself also has enough power to stop this easily.
Yes, It can . if bitcoin is accepted by government , I'm sure Bitcoin can make banks disappear at one. Now. there are many people using bitcoin for payment, purchase, trading online. It's easy and fast in transaction.
Why? Now let say the government accepts Bitcoin then automatically Businesses and related establishments will also accept Bitcoin because it is now legal in their country and that is including banks. Banks or Big companies can adapt to big changes and that is including the adaption of Bitcoin to their system. No tycoon will close down because of some kind of currency.