what happens if bitcoin builds a bank just like a bank with a headquarters, savings account management and also makes a bitcoin account card ??
I don't really see the purpose of such bank. The point of the whole thing is to be decentralized and this idea defies exactly this point. Only relation between the bank and bitcoin that makes sense (at least in this moment) is if the bank would enable you to directly change your crypto to fiat and vice versa - basically to act as a exchange.