That's a good point, and explains why there's a large brown cloud that originates over China and wafts over the world.
China has a population of 1.3 billion, the U.S. has a population of 300 million, but the land areas of the two countries are roughly equal.*
A chart showing "tonnes per square kilometer" would be interesting -- China would have 4 times the amount of CO2 emissions as the U.S.*
* Note: my back-of-the-envelope calculations didn't involve legitimate research.
Making that “per sq km” chart even more interesting, almost all of China’s production takes place in the eastern quarter (near the coast). Their pollution is really concentrated in those provinces. (Tibet ain’t exactly choking on the “dust”.)