But we are second in the amount of CO2 produced by country, albeit significantly behind China. However we produce more than China per capita since our population is so much smaller than theirs. Whether you measure it by pure tons produced or tons per person, we are a significant source of CO2 in the world. We have made agreements with other countries to work together to reduce but it is hard to get others to keep their promises when we won't. Everyone wants the other to go first
China is also first in emissions because they have pretty much zero regulations in place. That’s why a lot of manufacturing got sent there. Life is cheap. It’s cool if your food contains lead.
This MIT website doesn’t do a good job answering these questions. Some of these answers could have been written with more sympathy for the reader. As a person who was once paid to do jobs like this, I know what a thankless task it is because the people you’re trying to translate think you’re dumbing them down and the people trying to understand the scientists and engineers recognize that they’re speaking the same language, they’re just not using it in a way that makes any sense within the context of their lives.