Another thing to consider is the fact that the people will never be fully satisfied with any party to the fullest extent; there will always be faults based upon different views... there's no way to eliminate that. A multi-party system would cause more confusion than what it's actually worth. It's quite unfortunate.
Of course, but you were suggesting (or seemed to be suggesting) that the US has taken a more liberal view, which I may agree with if it weren't for arguments such as gun rights; a conservative view which most democrats fight for. The US is more moderate than anything.
Would we really want a multi-party system in the first place? Sure, a two-party system has plenty of downfalls. But, it does force candidates to moderate somewhat, representing a broad range of issues. Imagine if we had multiple parties, each dedicated to only one or two issues and not caring much about anything else.