its just if we have bank for bitcoin and then do through this all its better and safe way to use these cards every where
Of course that means that you have to trust the bank.
I suppose eventually there could be bitcoin banks that are insured by a government (equivalent to the current U.S. FDIC), and that are under strict regulation, but we are probably a long way off from anything like that. It isn't even clear yet if any government or major insurance underwriter would ever be willing to back any bitcoin banks.
The U.S. can't back BTC banks, because they can't print BTC arbitrairly.