Is the situation of a mom looking at her son's exam is exceptional in general in the US? Or is it common?
I think it has changed over time, and can be regional or urban/rural. I gather where I lived was a throwback to an earlier generation. My last exam with my mom watching was in 1992, and I was in a suburb of a second tier city in the South. Also my pediatrician was pretty old, nearing retirement. So I may well have been getting the 1965 treatment. I know other boys at that doctor had their moms watching their exams, because once when the nurse walked me down the hall in just my undies for weight and height at what I assume was the only scale in the practice, I saw another boy (fully clothed) and his mom being taken into another exam room. He looked to me like a high school senior, but even if he was closer to my age, he definitely was not the late bloomer I was. He was taller than his mom and had a manly build already. It's one of the reasons I was not surprised at all to have my mom come to my exams for a few more years.
But it wasn't just my doctor. One day a friend of mine who recently had transferred in from a bigger city leaned over to me when we were the first two back in the classroom after lunch and asked me quietly if I had ever gotten a sports physical (he was trying out for wrestling). I said no, just my annual check ups. He then asked if my mom came to them, and I said yes. He then asked if she was there when the doctor examined my dick and balls, and I said yes. He then told me that in his old city, his mom hadn't been to his exams since he started puberty, but she was there for his sports physical the day before, and it was the first time she had seen his dick and balls in years. Not understanding his embarrassment, since I was used to that happening every year, I asked if the doctor found a problem. He said, exasperated with my naivete, "With my dick and balls? No. You're not getting it." Then the other kids started to come into the classroom, so he stopped talking about it. He compared notes with at least one other friend of ours, because later that week that friend asked me, "Your mom comes to your doctor checkups, right?" I said yes, of course. And he said, "Yeah, mine too. [Our friend] acted like it's weird, but they must do things differently in [the bigger city he transfered from]. His also were at a hospital and not just a doctor's office." If our friend had found any other guys who agreed with him that it's weird for moms to be at teenage boys' physicals, I'm sure he would have told us, so I'm guessing it was normal in my town.