If you dig down a few layers through the US State Department website, you will come across a Press Release from February 2010 where the USA pledged to reduce its greenhouse gas emissions.
Press Statement
Todd Stern, Special Envoy for Climate Change Washington, DC
February 4, 2010
Special Envoy Stern: We are pleased to be among 55 countries – including all of the world’s major economies — that have submitted pledges to limit or reduce their greenhouse gas emissions under the Copenhagen Accord. These countries represent nearly 80% of global emissions. In supporting the Accord, we are taking an important step in the global effort to combat climate change.
In addition to the countries that have submitted targets or actions, a number of others have conveyed their support for the Accord. We urge all countries to join this broad coalition by promptly conveying their support for the Accord to the UNFCCC Secretariat.
The Copenhagen Accord includes important advances on funding, technology, forestry, adaptation and transparency. The United States is committed to working with our partners around the world to make the Accord operational and to continue the effort to build a strong, science-based, global regime to combat the profound threat of climate change.
I have commented on the commitment in previous postings, but just to be reminded of what was said, here is a copy of the letter sent by the US to the UNFCCC. 
Last week the US EIA released the latest greenhouse gas emission figures and they show that the country is well on track to meet this pledge, even though there is no formal program in place to ensure delivery. 
Following the sharp recession led drop, two continuing drivers for the change are the drop in coal emissions as older coal fired power plants close and the fall in automotive emissions due to tougher vehicle efficiency standards and the continuing higher oil price. As expected, natural gas emissions have risen as this fuel replaces coal in power generation, but with less than half the carbon footprint of the coal.
This trend could well continue over the coming years as further coal capacity is closed in response to the combination of EPA air quality regulation, expected greenhouse gas regulation and the growing supply of natural gas. In addition, CAFE standards should ensure further improvements in vehicle efficiency.
My original analysis of this trend produced the following chart. Two years on and we still seem to be at least in the same ballpark.
