You only need to look at Britain to see how much of a bad idea this is. As for CSAM I don't believe AI can't be used to solve that.

Age verification does not belong with app stores or OS developers. It belongs with the parents that are already legally obligated to protect their children. There is a simple means to do this [1] and while not perfect it would shift the responsibility back to the parents where it belongs. Texas should push for RTA Restricted To Adults headers on servers and RTA header detection in browsers and applications that speak HTTP(S).

[1] - https://news.ycombinator.com/item?id=48270018