Maybe this country focusing so much on keeping the gas cheap might have something to do with it.
American gas is not cheap. In absolute-numbers-sense, it's comparable to the current prices in Russia. And by all means and for all the different reasons, one would expect gasoline to be enormously expensive there right now. Far more expensive than in the States. It doesn't seem to be the case.
US emissions have declined 18% since 2005.
Look at Asia.