Are you kidding? The reason the terrorist attacked us is because of our Alliance with Isreal! And it is possible to have a democratic system without parties, although its a very rare occurance. People in my country (america) are close minded these days. At least half of them close there minds to new ideas, and only vote for "there" party, which is usually ethier Democrate or Republican.
You have a point about Washington. But even so, which is worse? Owning a few slaves and them setting them free after they die, or killing 18 million people? No, Washington wasn't perfect-who is? But compared to Stalin, he is an Angel.
They did not attack us ONLY because of our alliance with Israel, but also maybe because we impose our will as "World Police" with troops stationed all over the globe. We had attacked Osama before hand, and they wanted to show that they could strike fear into the worlds last superpower.
Most single party governments end in dictatorship, just look at history to see that.