In my experience, getting Americans to adopt Signal happened much quicker than WhatsApp. iMessage being a strong product and iPhones being so ubiquitous explains why WhatsApp isn’t the US standard, but the only way to explain Signal adoption is the combined privacy + encryption.

Europeans/LATAM/Asians/Africans are still predominately android, so WhatsApp makes sense.

This is all until there are encrypted messaging apps using Nostr!