I don’t understand what the problem is. There are a lot of advantages to having a low birth rate and fewer people as a result. It is rather obvious that the human population cannot grow indefinitely. At some point, 10 billion, 20 billion or even 100 billion, we just aren’t going to be able to muster the necessary resources and we are going to have to let a lot of people die. Even now, it is only the Haber process that let’s us feed ourselves.
All we are seeing is a reasonable response to economic cues. Children are increasingly expensive and it is harder than ever to offer them a better life. In fact, most Americans under 50 realize that their parents and older peers had things much better than they did. So, they are quite sensibly having fewer children.
It’s not as if this can’t be reversed. The baby boom, for example was a big surprise. The charts in this article show the declining fertility rate in the 1920s and 1930s. Experts were expecting the trend to continue, but when World War II ended people wanted to have children, and the government made a point of encouraging it by building housing, getting people well paying jobs, building schools and suburbs and so on.
If the US population actually starts falling, and it falls far enough so that we have actual labor shortages, then wages will rise and people will see a brighter tomorrow. They’ll have more money from those higher wages and more of them will use that money and other resources to raise children.