Indeed, I observed that among those of us qualified to teach the course, absolutely none of us had ever taken it. Here's what I learned about it, which may be unique to the US:

Just before starting freshman classes, the students took a math exam, and were sorted into three levels:

1. Calculus.

2. College Algebra, which like you say is a repeat of 10th grade algebra. Its curriculum is defined by the requirements for the minimum level of math that can be offered for credit at an accredited college.

3. "Remedial" math, which cannot be offered for credit, but is a preparation for college algebra.

I estimate that about half of the students were in calculus, and the other half in the lower two tracks. For all intents and purposes, if you're not ready for calculus as a freshman, you're not going to be a math or "hard" STEM major. It's the sorting hat. The opinion of the professors was that the algebra students didn't even belong in college, so the lower math courses were conducted under a black cloud. The rigidity of the accreditation requirements may have led to the rigidity of the curriculum, which I thought didn't belong in any century that I've lived in. For instance the course made no meaningful use of computers.

Since this was the state flagship university, the students represented K-12 math preparation throughout the state. The variation is huge. Some school districts offer two years of calculus. The high school that my kids attend has a deal with the university for kids to take college math classes beyond calculus. Some schools have no calculus. Some of the kids in my college algebra class had gotten A's in high school calculus, but somehow couldn't pass an algebra exam.

As a mathematician I may be the wrong benchmark but back in primary/elementary school (I do not know how you call it in the US) in a completey normal class at the age of 12-13 everyone understood the "two column format" and everyone used it. I guess maybe 10-20% of the class coudn't solve equations like this on the fly writing on the board in front of the class. And they were just slower and needed more time than the rest. This was shortly after the fall of the iron curtain in Western Europe.

I remember at the age of 12 being once in a math camp with a kid who used to live in the US before and he told us that the american kids in his class could not calculate the sum of 5 and 6 in their head. I thought this was just a mean joke. Until now.