edit: Also, one needs to separate the impact of the democratic system from that of the social/cultural system. A country with a very homogenous population tends to have less issues under any system of government.
I could also counter that the extra weight to "minority extreme views" is much less of an issue than most votes in most US states being meaningless because of the first past the post system on a state basis. But I don't really see this as a meaningful discussion, it's undebatable that the US system is flawed to the point where it can't be called a real democracy.