The only thing stopping "instant" swap to digital is so called "underground". You can't pay for child trafficking, weapons, drugs, and any other illegal stuff with fully trackable digital currency. Mafia and what not would be willing to either force "backdoor" for their business or take out few politicians here and there.
Thinking of emp, aren't most of server racks already in metal cases, installed in metal frames inside of metal warehouses ? Kind of wonder how much current would induce during pulse, while most of important infrastructure (IT infrastructure) is metal and grounded.