Looking at birthrates in other countries I'm not inclined to believe this phenomenon is limited to the US. In fact it seems weaker than in many other developed countries. I'm also not sure if I would call it selfish to decide against reproducing yourself. The other extreme of having children just because you want them for yourself and then not being able to give them proper opportunities is much more selfish to me. I think we should try to avoid moral judgements of people we don't know especially on something this intimate.

I'd be more inclined to agree with you if the language of people who eschew children weren't so often focused on their selves ("independence", "freedom", etc.) or simultaneously accusational ("how could you bring a child into this world!"). "Selfish" isn't a moral judgement in this case: it's an accurate description.

I think having children is pretty selfish also. You bring a child into this world... for what? To see yourself continued in the next generation? To make some future friends for yourself? To have that experience? How are these not selfish things? Both choices are selfish in different ways. The fact that one requires some personal sacrifice doesn't make it selfless.