Whereas affected the most, poor countries happen to contribute the least to climate change. Their emissions of CO2 equivalents per capita are way smaller than what wealthier nations have. The most affected are the least at fault. That’s where the saying “the rich become richer, and the poor become poorer” fits the best.
Because of the history and in a spirit of global fairness, poorer countries are given less strict conditions in the Kyoto protocol, as well as have lesser expectations imposed by the Paris agreement. However, the US uses this fact in favor of not adopting climate-mitigating policies, explaining that Washington can’t bear most of the cost while the poorer countries do nothing. This statement is obviously a misrepresentation of facts and should be taken by a wider public with a pinch of salt, especially that currently the US is doing the least on the political level to contribute to climate mitigation.