Google is not completely blocking adult sites, but Google is blocking adult sites due to their SafeSearch filter being enabled by default for users under 18.
Users can also turn on the Google SafeSearch filter manually or even a network administrator even an internet service provider could have SafeSearch filter enabled on their side.
You can often just disable the SafeSearch filter to access and search for adult sites.
If you're on a school network or work network or even other public Wi-Fi the adult sites may be blocked through them as well.
Parents can also use parental controls such as through Google Family Link, which can also lock the SafeSearch settings so they can't be turned off.
And some browsers and browser extensions also have built in safety settings and some browsers and browser extensions can be configured to block specific types of content.
It is also legal to watch adult pornography and view adult sites as long as you're a legal adult.
The pornography that is illegal to watch or possess including images and videos is child pornography which is different from adult pornography.
Federal law defines child pornography as any visual depiction of sexually explicit conduct involving a minor (persons less than 18 years old).
Child pornography is a serious offense and can get you into trouble and in prison for years for watching, downloading, sharing etc.
But adult pornography is legal to possess, watch, share, download etc.
As long as the adults are consenting to the sexual acts in the adult porn and they are consenting to share that adult porn online or any other way, the adult pornography is legal.
As long as the porn is not child pornography or bestiality, there's no legal reason that pornography cannot be filmed anywhere in the United States.
It's also legal to produce and distribute amateur porn with multiple licenses and insurance but you will need a release in most states if doing it as a business.
But you can legally film yourself and your partner or another consenting adult engaging in sexual activities and legally place that porn on adult porn websites without a license.