I'm from the Netherlands and I know plenty of people who have iPhones but I also know (and am) plenty people with androids. People use either WhatsApp or Telegram. Isn't iMessage just texting within a walled garden?
The situation is very different in the US, primarily because in other countries SMS fees tended to be really high a decade and change ago, and thus drove users to WhatsApp, but in the US most carriers had adopted some form of unlimited texting shortly after the iPhone first came out.
Thus, for many socio-economic groups, iPhone is definitely king in the US, and for them iMessage is just the default way to message people because when it was introduced it was the default way to use SMS on iPhone. A restaurant in Texas famous for their funny signs put this out, https://twitter.com/ElArroyo_ATX/status/1693316647677825160 , and tons of people (myself included) could immediately relate.
