I work in a job that has to deal with a lot of parents. These types are absolutely not uncommon in the United States. I have seen so, so, so many kids completely traumatized by their shitty parents or their parents' shitty religion, to say nothing of my own miserable experiences. I think a large part of it comes from, as usual with Americans, total arrogance. I think a lot of parents just assume they'll know how to raise their kids, and don't actually do any research or study into developmental psychology to try and understand good parenting habits. Being a parent isn't easy and reading literature is a great way to learn ways to be better at it. Considering how the concept of learning is under attack in the U.S., I don't think it's a stretch to say a lot of parents don't really know what they're doing, don't have any interest in doing better, and a lot of them end up being shitty because of it.