alt Hacker NewsAround 58% of American smartphone users are iPhone. It's a lot, but not enough to be universal. In my family there's 5 iPhone users and 4 Android users, amusingly similar to the national ratio.
Apple has famously made its strategy to use iMessage to enforce exclusivity. If you want to reach everyone, it's not iMessage. And Whatsapp in the US is worse, closer to 1/3.
What people miss about the US phone market is that while it's almost 60% iPhones, the vast majority of the top half of the income spectrum use them. I'm not sure if it's the same as it was a decade ago, but being excluded from iMessage group chats was a real exclusionary move for many teenagers.