But in developing nations, children are still seen as resources - the more the better. Without Social Security and Medicare, these people pay into the DNA pension plan, having children to support them in their old age. And to help them raise food, etc. Given that so many children die, people also want to have as many as they can to up their odds. But, at least for Americans, I think the notion of population control brings up images of China, where population growth has been controlled at the cost of individual freedom.
Most people find that to be a scary prospect.
American efforts to aid countries that are trying to reduce population growth often fail because we don't support one or more aspects of their program, so we refuse to fund any of it.