(Photo by tobo)
That's when you also notice that the whole US voting system is apparently expressly designed to be polarizing (winner-take-all electoral system etc). To somebody from Finland, that looks like a rather obvious and fundamental design flaw. In Finland, government is quite commonly a quilt-work of different parties, and the "rainbow coalition" of many many parties working together was the norm for a long time. And it seems to result in much more civilized political behaviour.
Of course, in the US there are also much wider social, educational, religious and economic differences between people, and issues range all over the map. Which then means that it's hard to bring up any nuances in politics, since either people won't care about them (not relevant for that group), or they simply won't understand them (what does "foreign policy" matter to somebody who has likely never been outside the US unless you count things like day-trips to Tijuana?).
So you couple a polarizing voting system with a campaign that has to make simplified black-and-white statements, and what do you get?
Ugly, is what you get.