Why is the USA political spectrum so narrow?

When we see so many different political philosophies in EU and other democracies why is that of the USA enclosed into conservative authoritarian?

Additionally, what would it take for the people to spread out and see the other parties grow.
Update: Senor Magoo, you're extremely wrong there. I suggest you do some research in the topic.
Update 2: Better dead: Go to my link. All demorats and conservatives are enclosed in the upper right of the spectrum. Americans have no choice, we're filtered in there and anyone who votes minor party might as well not vote.
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