Did the US have more than a tenth of the population being a Nazi or Stalinist in 2008?
No, but the US did not have an unemployment rate of 28% in 2008. And if the US had a multiparty system during the Great Depression with comparable unemployment rates, I have no doubt there'd be a substantial proportion of radicals.
My point is that the society is in real trouble. There's plenty of room for debate for why that is, but it seems hard to argue that the nation's tough economic times aren't a big reason why their political situation is so messed up.