[cosmie]

You don't have to have a global network to have global acceptance - RuPay[1] is a domestic-only network in India, but RuPay cards are accepted internationally via the Discover network. And the Fed seems to be heavily emphasizing interoperability with existing/external financial systems for FedNow, so there's no reason to think that wouldn't extend to interoperability/integration with international partners to extend acceptance internationally.

And even if they don't, siphoning off a huge chunk of domestic-only US transactions will still be a massive blow to Visa and Mastercard's revenue stream. And the ubiquitous nature of FedNow domestically could easily disrupt market dynamics, if/when it reaches a point of saturation where businesses can actively choose to not accept Visa/Mastercard payments. Squeezing their 40-50+% profit margins on top of reducing their revenue, as they're forced to actually be competitive against FedNow.

[1] https://en.wikipedia.org/wiki/RuPay