This isn't a uniquely American problem. Age verification is a huge pain to implement and completely tanks user sign up metrics. No tech company will do it unless absolutely forced by a major government, eg. see the recent US state-level laws that require age verification for porn sites. Websites are using IP-geo checks to apply the age verification process to as few users as possible.

Also I'd question putting Roblox in the child-friendly category. Hindenburg Research characterized the platform as a "Pedophile Hellscape". They obviously have a financial angle as a short-seller, but they point out some issues that seem pretty significant, in my opinion.

> We found Roblox to be an X-rated pedophile hellscape, replete with users attempting to groom our avatars, groups openly trading child pornography, widely accessible sex games, violent content and extremely abusive speech—all of which is open to young children and all while Roblox has cut content moderation spending to appease Wall Street and boost earnings.

> We put together a brief video compilation of Roblox moderation failures

https://hindenburgresearch.com/roblox/

Oh, I was wrong about Roblox. Some users even encourage 8, 9-yo to install Discord so they can groom them. So I guess there are two different issues here: porn sites showing indecent images and videos to everyone, regardless of age, and sick people grooming kids on social media and in games.