Why can’t everyone in these situations just ask everyone to use one app like WhatsApp? If having good experience was important everyone would be on board.
Also it's not a "good experience" for everyone, not as much as just cutting that green bubble loser out. With no green bubbles, you get to use the default messaging app. With a different app, since you can't change the default on iOS, you have to have at least two apps, and many people balk at that.
Are Americans just too lazy to download another app?
More I think they are just really susceptible to marketing efforts by companies like Apple who tell them that it's a bad user experience to have multiple apps, and your own personal user experience is supreme, so people adopt and believe that. And for the people who don't, you can almost guarantee they have at least one "Apple fanatic" in their circle who will preach that gospel to them routinely.
Then there's the social status symbol of "Apple" that has become a big thing in the US. The killer on top is the invasion of the social sphere, partiuclarly with younger people, where you are bullied and isolated for not having an iThingy, and you've got a perfect recipe for Apple.
At some point I think it's got to come back around, but unfortunately that time isn't looking soon as it's trending heavily in the wrong direction right now. It's so bad now that "iPhone" has come to be a generic word for "mobile phones" and "iPad" a generic for "tablet." Just a few days ago I heard someone say something like, "Oh is that an Android iPad? aren't those just cheap knock-offs?" When this is the level of thinking in most of society, it's not hard for a company like Apple to manipulate to serve their ends.
Citation needed? Apple has pretty much marketed the exact opposite (e.g. the entire App Store concept)
Isn't Google using a proprietary version of RCS? That's not cross platform.
Thats ignoring that some people (like myself) have philosophical reasons not to support Meta via WhatsApp. Just like others will not install Signal since it requires them to know your phone number (at least currently).
Then try a couple APAC countries, and people will ask why you aren't using LINE.
This has been going on for decades, ever since we saw AIM/MSN/ICQ and so on divisions country-by-country. In some cases it was simply who localized their app first.