The United States is not a Democracy? What an outrageous claim to make! Or so it would seem...
In fact, the United States of America is actually a Republic. The other terms bandied about amongst political scientists are "Representative Democracy" and "Constitutional Republic". And this isn't just a dictionary-zealot splitting hairs here; there are very important distinctions between a pure Democracy and what we have in the USA. And confusing the issue can actually lead to gross mistakes.
For instance, in the 2000 Presidential election, if you (hypothetically) didn't like George Bush but didn't trust Al Gore, you might have cast a vote for Ralph Nader on the belief that you were at least voting against the other two candidates. In fact, what you actually did was throw your vote away, because of the Electoral College system. Each state has a certain number of electoral votes, and the candidate who gets the most votes in a state gets all the electoral votes for that state, even if they only win by one vote.
Your electorate would have just counted the votes in your precinct until a clear winner emerged, then gone to the Electoral College and voted for the winner. That's what it boiled down to: one vote from each precinct. A vote for Ralph Nader did not cancel out a vote for George Bush.
In the more general scheme of things, the United States is a Republic because we have a representative government. Individual citizens do not get to directly vote on every detail, from whether we go to war to whether we have a seat-belt law. All we can do with a vote is appoint Congress members, Governors, Mayors, Senators, and yes, Presidents, too.
Once elected, those representatives can do whatever they please. They can say whatever they want when they campaign to get elected, but after you've voted them in, they aren't bound to represent you in the slightest. You can get them impeached for breaking a law or an oath of office, but there is no specific rule that says they have to keep every promise they made when they got elected.
Furthermore, in a direct democracy, the laws which are passed must be obeyed. In a Republic, the laws get interpreted by a third branch, which is the Judicial System. The court is free to throw out, rule against, or even just ignore a law if it finds the case is just and the law unfair. This is why everybody who commits adultery in California isn't in jail - there is a law against that, though, but it's ignored.
You're probably asking yourself, why is it that we don't have a direct democracy, then? Well, when the country was founded a mere 230 years ago, the device you're reading this on hadn't been invented yet. The same goes for cars, telephones, television, telegraphs, and radio. Where was communication technology when the Declaration of Independence was signed? The Gutenberg printing press. Ships on the ocean were sending signals by firing cannons and raising flags. On land, we had pen, paper, and the Pony Express.
Now imagine how long it would take to get anything done if we were to insist on collecting the informed opinion of every single citizen across the country in order to do every single thing, using only letters delivered by horse. You're right, it would be impossible!
You might now ask, "Well, now we can transmit information everywhere at the speed of electricity. Why can't we change to a direct democracy and throw out all of this red tape?" Not so fast! There are experimental ideas being tossed around about this already - one of them is the Unity08 party and another one is the National initiative to allow for ballot initiatives at the Federal level, being proposed by Congressman Mike Gravel, who is running for President in 2008.
However, even the boldest of these isn't proposing to implement a pure and full Direct Democracy right away. Do you, as a citizen, want to travel the world meeting with foreign leaders to decide if you want to do business with them or grant their request for aid? Would you have had the time to read every page of the hundreds of bills passed by Congress last year? And most of these on trivial matters such as how much funding to grant a program, what to name a bridge, whose face goes on the next commemorative coin, or who to appoint to the Spotted Owl Conservation Commission.
There's a lot to organizing ourselves as a group of 300 million people than you'd at first think. Simply put, we aren't built like ants or bees; nature didn't intend for us to act as a hive-mind. Humans are great in small groups, but even getting all of us together, such as in a Nationwide census or even in the Board of Directors at a corporation, is beyond us. Humans don't scale.
Humans don't scale. That's why we have the closest thing to a Direct Democracy - a Constitutional Republic!