Some people do know but it is waaayy more popular among inmigrants or for people who have family out of the country. But most americans do not know about it. Is the only texting i use.
We have it here but americans do not really use it. I knew about it from my friends and family (in venezuela) but most people i know here have it by now and it is all I use. I like it way more than text. They are missing out on the "read/ doble blue check marks" memes lol
I started using it because it is great if you have people out of the country you communicate with. You can text and call from the app and now i use it with my feiends here in the states too and have many group chats and it is great. In one chat i have friends that are here, latin america, australia and it is awesome!!!! Basically you can connect internationally for free send voice notes, text, send files and call.
This is everywhere in Mexico, you can't have a social life without WhatsApp.