One of the major factors to consider here is that public schools in the US are not equally funded by number of students. Instead, most of the funding is provided by state and local property taxes, meaning that richer areas where houses are worth a lot more, get much better funding for their schools. So while those rich areas’ school funding is probably much higher than the global median, the poorer areas’ school funding is likely much lower, in a very high cost of living country in general.
The other factor to also consider is that public schools in the US have fairly extensive athletic programs, meaning that they spend a lot of the funds to build and maintain things like American Football stadiums fields, swimming pools, etc., as opposed to only funding actual academic education.
Edit, I’ve retracted the link about teacher vs coach salaries because it’s about College sports, not primary and secondary schools. I still haven’t found a good source for this info regarding those.
PS: Aside from fundraisers, it’s fairly common to hear teachers telling stories of having to spend their own money to buy supplies for their classes.
PPS: It’s also common to hear stories of poor families doing everything they can to move to richer areas just so their kids can benefit from the much better-funded schools. I’ve even heard of situations where they will register their kids with the address of a relative who lives in a better-funded area, for the same reason.
Jeepers creepers, this is so disheartening. I’m sorry that you had to experience that!