If the US disable bank transfers then all other region will be forced to create its cryptocurrency or stablecoin as because the transfers will only be done using cryptocurrency. It will sky-rocket the price of Bitcoin. Do you think it will happen?
What did make you think of this?
Disable all bank transafers is impossible and unrealistic step. Governments can ask central banks to disable, freeze bank accounts that have any crypto related activities. There is no convincing reasons to disable, freeze or ban accounts that don't have any crypto tradings.
Bank transfers can gradually switch from fiat transfers to CBDC transfers but they will exist in human civilization.
The day when people only use cryptocurrency is far ahead and might never come. I see the benefits for the co existence of fiats, CBDCs and cryptocurrencies.