If you say just one or some banks maybe yes. but if you say entirely bank in the world would disappear because of btc I think it is not possible
some country even forbide the circulation of btc. how can bitcoin affect the bank in that country
Well only like 2 countries have forbidden bitcoin entirely so obviously so far most banks/countries do not care about bitcoin, it is possible in the future like 100 years but obviously not now. If everyone starts using cryptocurrencies then yes banks will eventualy disappear because we wouldn't need them.