Back in my young wild activist days, when I was involved in the pro-life movement, I learned that there is a terrible shortage of adoptable babies in this country. Since abortion continues to rage unabated, I doubt that has changed.
As for our "overpopulated" country -- (a) except for immigrants, we are below replacement fertility, and (b) have you flown over it lately?
Have you checked the price and congestion of ocean coastal properties lately. You know, the places where people really want to live?
There's only so much really nice real estate in this country.
As the population grows, a smaller and smaller percentage of Americans can be privileged to own that best land because there is only so much of it.
And they keep dividing that land into smaller and smaller parcels, packing people in so densely that the natural beauty of the places is ruined.
And so we become less and less prosperous.
A below replacement birth rate is a good thing, as we are already too crowded.