That’s easy: unlimited SMS was common on most mobile plans in the US as early as the mid-2000s. Unlike the rest of the world, Americans had no financial incentive to use WhatsApp.
We had unlimited SMS by the time smartphones rolled around in the UK, we still decided not having some weird caste system based on what messaging app you use was the obvious choice.
In fact I remember my American mates were charged for receiving texts, which I never heard of from any other Europeans, so I'd say there was probably a stronger incentive your side of the pond
@9point6@ardi60 Cross-platform, sure, but most are still controlled by single vendors, like the two billion people using WhatsApp (Meta), the 1.3 billion using WeChat, the 930 million using Messenger (Meta again), etc…
I find it funny it's called an American product as its iconic design was made by a Brit, CPU is manufactured in Taiwan and the rest is made and assembled in China
Most of my family here in Australia use iPhones, and by extension, iMessage. Granted, they also use FB Messenger, Snapchat and all the rest, but mainly iMessage. It's the default and it works for them.
I can assure you that this is not a thing exclusive to the US.