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 agree bad teaching practices can have knock-on effects (though I don't think knowledge of phonetics was at real risk of dying out?). But so can bad health outcomes, learning environments, etc?
I think, especially in education, that effect sizes are difficult to judge. And I can't find good data for reading ability over time. So I am very interested in what we are sure about/evidence is.