It depends on what you mean by "useful", in this scenario.

If by useful you mean that having multiple bank accounts will slightly increase friction for the government, when they attempt to freeze your fiat funds, then sure. But that's a losing battle.

Even with 100 bank accounts under your name, it would only be a matter of time until they shut them all down. All you are truly doing, is giving yourself a bit more time of breathing room.

You are attempting to protect yourself using a weapon they are in full control of, instead of using one they can never control.

People can choose to play hide and seek in the fiat world if they wish. Others would prefer to migrate to a new cryptographically secured space they cannot penetrate.