More (not so) fun facts:
54% of American adults read below a 6th grade level.
21% read below a 5th grade level, which is considered functionally illiterate.
High immigration numbers don't fully explain it either, as first gen immigrants only make up about 1/3 of those with low literacy.
I am autistic, and if someone doesn't have at least a rudimentary level of knowledge on important shit like politics, philosophy, science, etc. I'm not going to assume its because they are an expert in something else. I'm going to assume its because they are incurious and/or focused on fundamentally pointless stuff. They may or may not actually be interested in this stuff but its usually stuff that will gain them social advantage and financial benefit with other people also into said pointless stuff.
If one cares about the most recent celebrity gossip or gets angry when someone is a fan of a rival sports team, but say, shows no interest in the nature of dark energy & expansion of the universe or the effects of free will's lack of existence on justice: They are going to have an uphill battle to convince me they aren't a fucking troglodyte. Unfortunately, there are like, ten of these sorts of people for every one person who is the reverse.