This is common rhetoric from America's own left but it isn't entirely accurate, and is largely offset by the fact that American use of the term Liberalism differs vastly with the rest of the world and history. Actual socialist parties have waned to a barely marginal existence in most European countries, and often have at most a "tea party" like relationship to more center-left social-democratic parties. America's Democratic Party is closer to a European Social Democrat party than a centrist European Liberal Democrat party, as America's use of the word Liberal is far to the left of European use of the term. Many European countries have sizable centrist 'classical liberal' parties that would actually be considered 'to the right' of American liberals, oddly enough.

So no, America is not really a right and far right country, it's more a polity of extreme Conservative and progressive ideologies lorded over by two centrist parties with a heavily authoritarian commonality between them. What the U.S. entirely lacks is an anti-authoritarian centrist Liberalism akin to that in Europe.

To illustrate, if we were to align US parties to those parties in the UK, you'd likely get the following: the conservative Republicans (US) align to the conservative Tories (US), the far right Tea Party aligns to the far right UKIP (UK), the progressive Democrats (US) align to the social democratic Labor party (UK), and then the UK's centrist Liberal Democrats do not align to any recognizable political organization in the US. The UK Lib Dems at best might loosely align to a combination of US civil libertarians and classical liberals, both of which belong more or less to the politically homeless. Some might say those fall under the Democrat tent, and yet the most vocal proponent of civil liberties in the US government right now is conservative Rand Paul, so go figure.

To come full circle, a US equivalent of the UK LibDems, were it to exist, would likely be the most vocal opposition to the NSA.

Appropriate username btw :)

[Citation Needed]

To be sure, a thorough examination of social conservative thought will be fascinating reading.