The National Literacy Institute makes the claim.
Literacy Data and its impact on the Nation
- Illiteracy has become such a serious problem in our country that 130 million adults are now unable to read a simple story to their children
- 21% of adults in the US are illiterate in 2022
- 54% of adults have a literacy below 6th grade level
That seems impossible, given the demands of a modern society.
Note that this question asks about current adults, not about educating children.