I'd also like to suggest that people find it easier to be angry at losing than making an effort to win. Directly related somehow.
This. You are given the opportunity to vote for your elected representatives and leader. There is no threat of violence, discrimination etc for voting for the wrong choice and the results of the votes are honoured without, much, electoral corruption.
America is a democracy. It's pretty pathetic that people who are too apathetic to actually do anything to get candidates that they support elected simply wash their hands of it and claim the system isn't democratic. It's like someone saying that it's all the supermarkets fault they are fat because they position the food and you can't expect the shopper to take some responsibility for picking the right foods for them.