The 2-party system that characterizes America seems to lead to a politic that agrees on little, and never agrees on anything substantive. Even good ideas are opposed first and examined second. When the opposing party proposes an idea it seems that politicians feel it their duty to find evidence against the proposal instead of trying to find the truth. A prime example is President Bush's Social Security privatization plan. His approach was very open and inclusive - identifying an acknowledged problem and asking for help from both sides of the aisle. Instead of help, he immediately dichotomized the hearers into camps, and he was immediately criticized by the left and praised by the right - and this before any details of the plan had been released or even decided.
The source of this problem is the interplay between our culture of immediacy and a first past the post electoral system. As the name implies, our system leads to a horse-race style of politics, and eliminates all but the top two parties. The unintended consequence of this system is to make every issue a part of the competition. Unless there is unanimous national support for a position, it can be almost assured that the parties will take opposing positions.
This dichotomy is furthered by the immediacy of the news media. For example, the media expects a response to presidential State of the Union addresses 5-10 minutes after the speech is over. This is not enough time to think about and digest what has been said, and the opposing party feels disposed to focus only on that which makes their party look better and the president's look worse.