The Illinois bill is not about 18+ content. It's about controlling who your children can talk to on social media. The OS age check is just a means to that end. The end is blatantly unconstitutional. The bill of rights doesn't mention age limits. Freedom of assosiation applies to kids just as much as it does to adults. If the bill passes, then any racist parent could block all comms from kids of a different color for example.
To be fair, as a parent I don’t want my under age children hooking up with literal nazis on social platforms, whoever that might be. The current tools and controls are lacking. A lot.