Banks own and control cash, it's a centralized system out of the people's control already. Pointless to fight for that. Gold and silver coins would be more realistic, but since the stores goes cashless too you're limited to digital assets. Which leaves the banks, or crypto as the only choice.

Crypto is the most strategic choice, the country has some of the worlds best internet coverage and plenty of energy sources. Big box stores and banks will collapse long before the connectivity or the grid becomes unusable, and the day any of the grids goes down, no medium of exchange matters.

People would starve and freeze to death in days, so you really don't need a currency for a SHTF situation, only food, firewood and a couple of guns, all in a strategic location you can easily defend from an army of zombies.