I really doubt that, in my subjective experience the average person doesn't care about any of those issues enough to be depressive about them and certainly not

I really doubt that, in my subjective experience the average person doesn't care about any of those issues enough to be depressive about them and certainly not enough to commit suicide over climate change or political extremism. Gen Z kids aren't nearly as "political" as the millennials working in media want them to be. The average teenager doesn't care about affording a house or the political climate, I think you (and a lot of others) are projecting a lot of your own fears onto them. It's also worth noting that the US is not the whole world, there are European countries which deal with the same mental health crisis in teenagers despite being a safe haven even in the worst climate change scenarios and have a quite stable political situation.