I am an American, and I remain optimistic that we can fix our politics. In fact I'd say that fixing our politics is exactly the same as manifesting political will. For a generation since the labor movement dwindled there have not been any significant vehicles of popular will at work in American politics. It's past time to change that. To suggest we can't is simply despair - it will be true as long as we believe it, and no further.
I think you don't understand the American political system. At present there are only two parties in terms of realistically getting elected. There is no such thing as a ruling party in the sense of European parliaments. Members of a party are free to vote as they please. Hence Lieberman famously derailing aspects of Obamacare. There is also the fact that both parties in the U.S. have shifted very much to the right the last 40 years. The reality in the U.S. is that even with our so called left leaning party in power in the legislative branch and executive branch no serious environmental accords were negotiated and passed.
The resource consumption per capita of a person in the U.S. far exceeds the resource consumption of a person in Afghanistan. One American is more damaging to the world wide environment than a family in Afghanistan. Thus your second statement is not relevant. It is true that Americans have fewer children than people in poor countries. But our overconsumption more than makes up for this deficit.
It really only requires political will.
Are you an American? Because this statement sounds like someone who is not aware of the political reality in the United States.