It's the status symbolism of the green bubble vs blue bubble. Here in America we try to show off how rich we are by driving fancy cars, live in giant ridiculous houses, and buying all the latest most expensive tech the day it's released.
You can see me in a fancy car or in front of my mansion, but how do you know i spent way too much money on the phone i text you from? If all texts arrived on your phone in the same color you wouldn't be able to immediately identify which kind of phone i sent the text from.
Now here's the magic: if i send your iphone (bc let's be real, if you don't have an iphone you aren't someone worth talking to) a text, you know it came from an iPhone because the text bubble is blue. If you ever received a text and it was this hideous radioactive snot/puke green... Just delete. Just don't even bother. I can't believe I'm even typing these letters, it feels so gross... But that green bubble means you received a text from someone with an.....Android. 🤮
Most Americans aren't obsessed at all. They just want to use whatever is easiest, and iMessage is preinstalled and mostly works fine with pretty much everyone. The bias toward default is strong.
It's because texting has been very cheap there for a long time. It's now very cheap where I am too, but in high school everyone was using stuff like MSN Messenger where possible. At that time teens in the US were texting. It became cheap where I am by the time WhatsApp came out, so we have a mix of WhatsApp, Facebook Messenger and texting