What did you find? I only see a global number, but this proposal requires 100million MUA in the USA
With some quick searches, multiplying iPhone's 39% marketshare with 328million Americans gets me to 127million, but that's probably too high - not everyone has a smartphone, and how many users actually use iMessage at least once a month, and not say, WhatsApp exclusively ?
I have a hardtime imagining users with a MacBook or iPad but not having an iPhone adding a significant number of iMessage users
But the question was if there are a 100 million MAU in the US, let alone how to find that information in a simple google search. I couldn't find any breakout of iMessage users per country
With some quick searches, multiplying iPhone's 39% marketshare with 328million Americans gets me to 127million, but that's probably too high - not everyone has a smartphone, and how many users actually use iMessage at least once a month, and not say, WhatsApp exclusively ?