That's hardly an argument in case of US. Afteral folks out there aren't sharpest pencils...
On average, 79% of U.S. adults nationwide are literate in 2024.
21% of adults in the US are illiterate in 2024.
54% of adults have a literacy below a 6th-grade level (20% are below 5th-grade level).
https://www.thenationalliteracyinstitute.com/2024-2025-literacy-statistics
You'd have to ask the literacy institute...