The US has a below-replacement (collapsing) fertility rate of about 2.05 children per completed family size; but there are plenty of "poorer" countries which have an even lower rate:
Iran 2.04
Tunisia 2.04
Bahamas 2.02
Chile 2.00
Brazil 1.90
Sri Lanka 1.88
Mongolia 1.87
North Korea 1.85
Thailand 1.83
Azerbaijan 1.67
Trinidad and Tobago 1.61
Cuba 1.49
All these figures are from the UN Total Fertility Rate ranking online.
Even the countries with a much higher fertility, also are seeing rapid drops in that rate --- for instance, Namibia, which went from 4.89 to 2.57 between 2000 and 2010, a phenomenal 10-year drop. Tthe trend is downward, globally.
The problem isn't "3rd world countries breeding like rats." The problem is crappy economic/political systems which penalize productivity, strangle enterprise, and incentivize dependency. Something that's going on right here, right now, right in the USA.
The fear of the Lord is the beginning of all wisdom and clearly the “depopulation” proponents are godless and lacking in all wisdom and reason. The Bible states that children are a blessing and debt is a curse, but our public policies are exactly the opposite. We rack up insurmountable debt while we promote reduced reproduction. The consequences will be painful.