Is it? At the start of the election there were approximately 20+ presidential candidates, with around half having a reasonable chance of being elected. Four major candidates (Sanders, Trump, Stein, Johnson) were essentially unaffiliated with the major parties, though two ran for the respective party nomination.
And even though two parties dominate Congress, members are much more undisciplined when it comes to voting along party lines than in PR-based systems. Hell, have the Republicans don't even support their nominee. American democracy is messy but vibrant.
Well, two candidates have a possibility of winning. The nature of first-past-the-post elections means that Gary Johnson or Jill Stein can still affect the outcome if their votes change the result.