EDIT: In any case, even if most people use only ballpoint pens, it seems very hard to live without ever crossing a fountain pen user (as seems to be the case for the author of this article).
In the US, fountain pen use is common among people who have a particular interest in pens (e.g. collecting them), and almost zero among everyone else. I’d say they’re roughly comparable to mechanical keyboards in this respect.
No one at any level of school is required to use fountain pens; typically, students use a mix of graphite pencils, ballpoint pens, and rollerballs.
I would expect a large fraction of Americans, maybe even the majority, to be surprised to learn that fountain pens are still in common use anywhere in the world.
Gel pens feel so much better than regular ball point pens and are still almost as cheap.
People even draw with them.
Err, "an improvement" probably needs clarifying, though. It moves across paper much more smoothly than the ball point pens I've used, and I find reloading the ink to be enjoyable (I've also gone two years without the pen disappearing into the void, something which has never happened for me when using disposable pens). It does seem like fountain pens require heavier paper than ball-points, though. Maybe it's the ink I bought, but trying to write on the standard lined paper used in schools leads to a lot of smudges and bleeding ink. Standard weight printer paper is fine, unless it was left out on a few humid days.