There are a lot of cross platform messengers out there in the market, if the US market is tired of using a proprietary messenger that’s only available on one platform, they can always switch to many of the very popular platforms, and most of them are cross platform. Being not in the US I find it very interesting that Americans still relies on SMS (iMessage is a messenger built on top of the SMS app in essence) so much.
I can simplify it for you.
I like to think I am what you would consider a trendy american. I am definitely not a flag waving "God save America" fanatic like the media would make you believe lol. I am nearly 30.
I do use SMS and iMessage regularly just because in America we are wired to trade numbers and "I'll send you a text" when we meet someone.
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HOWEVER, macrumors and the internet will have you believe that we care about bubble colors and never use any apps outside of iMessage which is an exaggeration of epic proportions.
I use iMessage regularly with friends and family and coworkers.
I also use snapchat to communicate with friends that are younger than me or relatives like my little brothers who are 17 because it is easier to get them there to respond.
I am what you would consider an influencer i guess so i tend to use Instagram and tik tok as well.
I have friends all over the world so we mainly use whatsapp and telegram to stay in contact.
Back in my early teens and 20s, i used to be heavily into K-pop (Korean Pop). Not as fanatical as I was then lol but i do listen to it now and Kakaotalk is a Korean prefered chat platform we used to talk to other K-pop fans. Bubble is another app that is popular.
THe point being is that Americans do use plenty of other messaging apps and communicate in more ways than iMessage/SMS. They simply need a reason to do so and most of us have at least one or more social media/messaging app so it's really overblown