I feel it's unfair to be blaming phones, social media, and multiplayer video games for being the way teens get some peer socialization in a world that is so deeply unfriendly to teens having independence.
danah boyd spent a bunch of time studying teen use of earlier social media, and then for personal reasons moved on to help run teen crisis text hotline.
Her thought for why US teens are struggling are the lack of non-parent trusted adults in their lives.
"Struggling with a Moral Panic Once Again" https://www.zephoria.org/thoughts/archives/2024/04/19/struggling-with-a-moral-panic-once-again.html
There's also some evidence that it's mostly teens on wealthy English speaking countries that are the most depressed.
"America’s Top Export May Be Anxiety: English-speaking teens are spreading their problems abroad." https://www.theatlantic.com/ideas/archive/2024/06/mental-health-crisis-anglosphere-depressed/678724/
I have long thought modern American kids have too little freedom to go places on their own.
"This article is more than 8 years old: The popsicle test: what makes a city good for children?" https://www.theguardian.com/cities/2015/aug/21/city-good-children-popsicle-test-crime-property-play
I blame the young earth creationist christians who think that humans are incapable of destroying gods creation, and that the increasing planetary instability means that god will return and put them in charge any day now.