I didn't claim that Americans understand politics in other countries that well at all.

I'd be more than happy to bet that they are typically a lot better informed than you'd guess

And yet every person I've talked to who has an outside-looking-in view of US politics was positively stunned that Trump won the election. Their left-leaning news sources and celebrities absolutely convinced them that there was no way that America would elect Trump. Once again, they didn't understand American politics as well as they thought they did. Rather than admitting their ignorance, they tend to rationalize.