I think there are two main things that demonstrate that the USA, with their virtues and defects, are an advanced democracy.
On the one hand, I think it's really important the fact that someone who has voted for a Party (even he has supported its campaign or has taken part of a government) can change his vote in the next election. The best example is Colin Powell, who was the Secretary of State with George Bush and has said he'll vote Barack Obama. I think it reflects a great citizen responsibility. And it's really inconceivable in Spain.
Besides, every member of both cameras of the Congress is supposed to defend his own principles. He's not subject to the Party's discipline because he has done his individual campaign and he has been elected because of his own ideas. The most recent example is the voting of the plain against the financial crisis, where a lot of members of the Republican Party have voted no to the plain that has suggested his "leader".
On the other hand, I really like the fact that both main Parties discuss the most important reforms. Although one of them has the power to approve the laws without the support of the other, they try to reach an agreement before. So, they make sure the main laws won't be changed in the next session.
It doesn't happen in Spain, where every change of government means the destruction of the work that the last government has done. For example, last government was working last years in an education reform. When it was prepared to be voted, they lose the election an the new government threw away it and made another one completely different. It wouldn't happen if they had discussed it before.
As opposed to Spain, in the United Kingdom, where there is a democracy as advanced as it is in the USA, the ex-leader of the Labour Party Tony Blair went on with some of the policies of the conservative Margaret Thatcher. If something worked, why did they have to change it? Only to get some votes? No, they knew the nation is more important than the fact of win the election, something that Spanish politicians have forgotten time ago.
James Wilkinson