Cross-messenger groups are not a thing between WhatsApp and any other messaging app, your snark isn't helping any point.
"The rest of the world" is also not the whole rest, there‚a China, Japan, Korea, with WeChat, KakaoTalk, ...
"The rest of the world" is also not the whole rest, there‚a China, Japan, Korea, with WeChat, KakaoTalk, ...
But what I wanted to highlight is that SMS/MMS and generally carrier-based messaging is just as much of a weird communication island at this point as all of these OTT messengers are, from a non-US point of view.
RCS would just be a continuation of that, so I'm not sure if it's worth cheering on Apple for taking this path, further cementing Google's hold on Android messaging in the US – they run almost all the infrastructure and get all the message content, after all!
So, won't help with Americans or any other part of "the rest of the world".