Other contributors have said "What country has the highest CO2 emmissions?" is the same question as "What country has the highest CO2 emissions?" If you believe that these are not asking the same thing and should be answered differently, click here
CO2 = Carbon Dioxide. This is the gas that plants breath is part of make-up of the atmosphere. This is why it is important to replace the trees when they are cut down. Also humans exhale this gas....
the united states of America uses about 20 - 25% of the worlds carbon based fuels per year and are the second largest user of coal for power (next to china). But our overall carbon emissions are far...
They differ from country to country in many ways. Depends really on what you are actually looking for. See links below to get more info on global CO2 emissions.