The US is very middling in this data. PIAAC is a global measure (conducted every 10 years, so we are coming up on another data dump), and they compare data across countries.
So as you read a stat like this, I want you to understand: this isn’t unique to the US and thus isn’t indicative of a challenge unique to the US. There is a reason educational access is one of UNESCO’s Sustainable Development Goal. Additionally, women and POC are over-represented in the data, unsurprisingly.