Most countries have far too many people to begin with and could do much better with fewer. For damn sure the US. Population was 140 million when I was born now who knows..somewhere north of 300 million.
Few, if any, think they are part of any "surplus."
Each has his own purposes, however far his "liberty" will take him in his "pursuit of happiness."
I suppose "we" (the human race) "need" a certain number if we're going to colonize Mars, or perhaps the vast ocean floors which are 70% of the surface of the planet.
Just a thought.