What are you smoking? Access to porn has been legally restricted in every state to 18+ for decades. Adding the Internet only made things easier because nobody enforced it the same way they were already enforcing brick and mortar stores that had the exact same materials.

Likewise, there are plenty of rules and regulations around adult content on broadcast airwaves managed by the FCC.

Challenging adult content as "free speech" has happened and already settled precedent at the Supreme Court.

Yes, individual states are still trying to figure out how to actually best enforce the laws on the books at the Internet level, but there's no pretending that it is just a few states that actually have those laws.