having less children if you live in a developed economy just means outsourcing your children to a developing economy.
If there are 1 million less children born in the US, it's very likely there will be 1 million more immigrants to take their place, and the places those immigrants come from will have higher birth rates to replace them
If there are 1 million less children born in the US, it's very likely there will be 1 million more immigrants to take their place, and the places those immigrants come from will have higher birth rates to replace them