According to the PIAAC, 54% of Americans are illiterate. That is, they are able to read simple things like menus, but they are not capable of synthesizing new information from multiple texts, or understanding the nuance of an authors argument. If I recall correctly, Americans scored an average of around 275/500, while the best scoring country, Finland, scored an average of 300/500. (This is a statistically significant jump, and causes a huge portion of those in Finland to not be considered illiterate, but they just begs the question of why the literacy cutoff is where it is.)