Doesn't even need to be a war that causes problems here. This:
> - Shutting down only Visa and Mastercard would disable the vast majority of credit cards.
Happened in the UK and Europe in June this year, where Visa's network crashed and took out credit card payment processing for millions of people for a good day or so:
As you can guess, that caused absolute chaos, with the crash becoming a major news event and many customers and businesses being unable to spend/receive money at all until it was fixed.
So yeah, forget a government. Even a large business like that crashing or experiencing major technical glitches for a few days or so would bring down a large portion of society.
The UK also had the NHS crypto ransom attack. It's hard to say if the US is similarly vulnerable, on one hand the US hospital system is more heterogenuos, on the other, the hospitals in major US cities have very janky IT systems.
Actually, the majority of hospitals and trusts had little to no infections in that attack, obviously some (too many) did which is why it was bad news. But the NHS, in IT terms, currently operates as a disparate set of trusts with mostly their own IT systems. The reason that there was the level of infection there was, was due to lack of national IT standards/systems being enforced and trusts using outdated unpatched systems. The few national systems in use are, while not perfect, much better funded, updated and secured.
> - Shutting down only Visa and Mastercard would disable the vast majority of credit cards.
Happened in the UK and Europe in June this year, where Visa's network crashed and took out credit card payment processing for millions of people for a good day or so:
https://www.theguardian.com/world/live/2018/jun/01/visa-outa...
As you can guess, that caused absolute chaos, with the crash becoming a major news event and many customers and businesses being unable to spend/receive money at all until it was fixed.
So yeah, forget a government. Even a large business like that crashing or experiencing major technical glitches for a few days or so would bring down a large portion of society.