Agree - WhatsApp is super popular here in the UK, around Europe, and many other geos. I realise that it doesn't seem to be that popular in the US (and possibly) Canada, tho.WhatsApp has a lot more brand recognition in areas where it's popular, and it's been around a lot longer. If anything, messenger should merge into WhatsApp.
I only use WhatsApp when travelling, aand to keep in touch with some foreign exchange students that we have hosted over the years, but it's a nicer app than Messenger and I wish it was more popular here.
Rebranding it would cause an outcry similar to the Twitter / X debacle...