I mean for context, in those countries Meta paid to setup these networks. They're not a government-enforced monopoly, you're more than welcome to start a competing network.
Countries like Mexico or Spain have adopted it as the default form of messaging. Only today I used it to chat with our lawn maintenance guy, our car washer, and someone who's repairing our espresso machine.
I could maybe try to convince friends and family to use another app but I won't be convincing an entire country.
SMS is not an option because, again outside of the US, people pay by SMS sent.
There are plans for Whatsapp interop but probably only in the EU.
https://www.wired.com/story/whatsapp-interoperability-messag...