data point: "China in 2000 accounted for almost 15 percent of emissions, but its per capita emissions were less than one-sixth that of the United States."
from http://www.nytimes.com/aponline/science/AP-Canada-Climate-Change.html
I expect India and Africa would have much lower per-cap emissions (lower than one-tenth), Latin America higher, and rest of Asia a mixed bag.
I could be wrong that "most" Third Worlders have less than one-tenth of US emissions. Certainly most have less than one-sixth though.