Additional context for some perspective on what the number means:
"The US literacy score between 2012–15 was 272 — right above the international average of 267. Other countries in this realm include Denmark at 271, and Canada, Korea, and England at 273. The two highest-scoring countries were Japan at 296 and Finland at 288."
It should be noted that there are a ton of native Spanish speakers in the Southwest who show up in this data with very low English literacy but who may have higher Spanish literacy
I was thinking the same thing and then I wondered what the scale was measuring. Turns out it's on a scale of of 0-500. So New Mexico's 251/500 isn't so bad compared to New Hampshire's 278/500
Really it shows that people are dumb everywhere, which I'd agree with.