The entire political spectrum outside the US is much broader, whereas the US political spectrum is very narrow - and goes between centre right, and far right. Outside the US's two party system, you can literally have communism, fascism, left wing ~anarchists, fundamentalist religious groups, ultra capitalists, status quo centrists, etc - all on the same ticket with a ~real chance of winning.
So it's not to say that the US has a monopoly on far right politics, but that the US has a narrow political discussion between choosing far right groups (tea party minarchists, ultracapitalists like Koch/Trump, religious fundamentalists) - or choosing what would still be right wing centrists by any other countries standards (Hillary, Barack, Bill, etc).
For comparisons sake, you may have heard of Justin Trudeau to the north - as though he's some sort of looney left wing candidate? He's actually our centrist party, to the left of him is the NDP - which was the runner-up party (if we didn't go with Justin, we would have gone even further left) - and beyond the NDP is the Green Party, and beyond them is the Socialist Party, and beyond them - Canada used to have a literal Communist Party (who was actually advocating abolishing private ownership, and they used to get a couple percent of the vote).
Here is the US political compass this election:
https://www.politicalcompass.org/uselection2016
Here is the earlier chart from during the primaries:
Virtually the entirety of US politics is concentrated in that Authoritarian Right quadrant (blue), and usually it's even within the upper right quadrant of that quadrant. This is a weird year, because Trump is unusually Left (economically) for a Republicans candidate, and Hillary is deeper to the Right economically than Barack or Bill (both were exactly in the middle of the blue quadrant).