It's not odd at all.
Lots of iPhones in the US because of high incomes, and high iPhone availability. Lots of non-iPhones in the rest of the world because of comparatively low incomes, and significantly less iPhone availability.
I see no mystery.
Also, Americans were using awful phones while the RoW was using much better phones like Nokias thst even in their non-communicator series made texting far easier thanks to stuff like T9.
So the rest of the world used SMS and texting far more than Americans Pre-smartphone.
When smartphones came out and WhatsApp was released, the RoW was far more willing to pay the dollars needed to buy WhatsApp (it wasn’t free before FB bought it) because they would easily save on their low but still not free SMS charges.
Whereas Americans were not as willing to pay for an app to do something they didn’t do anyways, and anyways by this time phone carriers in the US made SMS free for the most part.
As a result WhatsApp became entrenched in the RoW well before iMessage was released (2011), so non Americans continued using WhatsApp, even as Americans started using the free available iMessage instead.
Worth mentioning the unique phones sold in the Japanese market by domestic manufacturers prior to smartphones, which were some of the most advanced in existence at that point and had been for many years. People in Japan were doing things on their phones in the late 90s and early 00s that most of the rest of the world wouldn’t for another 10-15 years.
Americans definitely used Nokia phones in the 2000s btw, not to mention Asian ones like LG, Sony, etc. I never saw a cell phone in the US that didn't come with T9 word and by ~2008 full QWERTY keyboard phones were extremely popular. Texting was very easy in America in the 2000s and we did a lot of it.
The dollar was often waived. They were never serious about charging non-business users.
The US is not the only country with a wealthy populace which tends to use mostly iPhones. The UK, Germany, Switzerland, the Baltics, Japan, South Korea, Singapore, and Taiwan are all roughly equally as wealthy (if not more so) per capita. However, in literally everywhere else but the US, people almost exclusively use third-party apps like WhatsApp, Telegram, WeChat, etc. iMessage is completely ignored, and the Messages app on iPhones is used solely for SMSes from carriers, 2FA OTPs, and random spam that is ignored.
Furthermore, several flagship Android phones rival iPhones in cost now.
Are you thinking of GDP, perhaps? I think that household income (and individual) is highest in the US (adjusted for PPP).
https://en.wikipedia.org/wiki/Disposable_household_and_per_c...