Maybe where you went to school. I always had Fs at 59% and under… just like in Wikipedia’s article. https://en.wikipedia.org/wiki/Academic_grading_in_the_United_States
I attended and worked in a couple schools in the states. I saw some alternatives like pass / fail and SBG, but whenever it was the A-F system, 60% was a D-
I would argue under 60 = F is the norm. It’s even quite a common trope in movies / TV. Example:
https://collider.com/the-simpsons-bart-gets-an-f/