It is hard for international observers of the United States to grasp the political paralysis that grips the country, and that seriously threatens America's ability to solve its domestic problems and contribute to international problem-solving. America's governance crisis is the worst in modern history. Moreover, it is likely to worsen in the years ahead.

The difficulties that Barack Obama is having in passing his basic programme, whether in healthcare, climate change, or financial reform, are hard to understand at first glance. After all, he is personally popular, and his Democratic party holds commanding majorities in both houses of Congress. Yet his agenda is stalled and the country's ideological divisions grow deeper.

Among Democrats, Obama's approval rating in early...