Read the linked source.

the religiously unaffiliated share of the population, consisting of people who describe their religious identity as atheist, agnostic or 'nothing in particular,'

Many of the unaffiliated retain religious beliefs or practices without affiliating.

One fifth of the US public and a third of adults under the age of 30 are reportedly unaffiliated with any religion, however they identify as being spiritual in some way. Of these religiously unaffiliated Americans, 37% classify themselves as spiritual but not religious.

Affiliation is about which community you are affiliated with. It's not about beliefs at all, actually. Affiliated means "I would call myself an X", and if you are not affiliated with a certain group, you are not affiliated, no matter if you are atheist, agnostic, spiritual but not religious or even religious but not strong enough to actually affiliate with one group.

Remember, atheism is a belief in itself, contrary to agnosticism. Atheism is the conviction that no God exists, even though there's no proof for an absence of a God. Agnosticism on the other hand is acknowledging that there is no proof that God does or doesn't exist, so they just don't care about it.

Atheism is in many ways similar to a religion. There are communities formed around the shared belief that God doesn't exist, they preach that God doesn't exist, they study their literature to find proof that God doesn't exist. They defend their faith that God doesn't exist, like any religious person would defend theirs. There are even atheist missionaries who stand on street corners preaching that God doesn't exist.

To be an Atheist is to believe so strongly that God doesn't exist that it becomes something like a religion in itself, and that's rather rare.

Agnosticism on the other hand is really wide-spread, even within religiously affiliated people. There are tons of religiously affiliated people who are socially religiously affiliated but are actually agnostic ("All my friends and family are X. I don't really care whether God exists or not, I don't really believe in the spiritual teachings of my faith, but I'm not that much at odds with it that I can't live as an X, and denouncing the faith would lead to repercussions, so I'll just formally keep being X, because it's less hassle.").

Clearly 24%(=89%-65%) of the population with a highschool degree give the impression they don't have it.

Tbh that seems fair, perhaps a bit low :D.

That 3% atheist figure is drastically lower than the global 10-15% and probably misleadingly low because identifying as an atheist on a survey and functionally being an atheist aren't the same thing.

I understand that no religion =/= atheist, but when you look at these other 'atheist adjacent' stats like "no religion", they don't reflect a population that's as religious as "3% atheist" would suggest.

We're probably just seeing problems with the word atheist in the US, not a true accounting of how religious people are here.