Your 401k, IRA and your savings account are exactly the same. However with Crypto you can easily protect from this problem with a hardware wallet like Ledger.
If the entire web is down, no transactions can be made because no miners to approve them so that hardware wallet is useless. Of course the entire banking system would be down too. That’s when you’re going to have to have cash and hope that people take cash. Else you better have something to barter. Gold, silver, lead & brass, food, water.