But that is the root of the climate crisis. When it was just 150M Americans living a developed-world lifestyle, the climate was fine. As soon as you broaden that out to the 8B+ people living today, allowing all the folks in China/India/Africa to have the same lifestyle as the West, you have problems. In 1960 the average American emitted 16 metric tons of CO2; China emitted 0.5 metric tons and India 0.2. In 2020 US emissions actually decreased to 13.8, but China is at 9.2. Per capita emissions can decrease modestly but if you increase the number of capita by 50x, total CO2 emissions will increase accordingly.

Likewise, the climate crisis is far more likely to be solved by WW3 reducing the population down to ~1B than by individual per capita reductions.