To start I was very intrigued by the question posed by Great White Snark, "Why, why, oh why on this blue and green Earth, are you so proud of your self-enforced ignorance, active lack of knowledge and general idiocy?" For myself as a US citizen it is something that I have thought about often because it affects the lives of many people and reflects badly on us all. In short the US media, political system, culture, and history have all led to a group of people who are ignorant and angry. While it is hard to determine whether this group in the US is larger than similar groups in every other region of the world it is clearly more vocal. Let us hope that we can be a example of what not to do for the rest of the world.

To preface this I am no expert in US law, politics, or sociology. Furthermore, there is likely no truly correct answer to the question posed and so much more could be given than what I have here, but this is my considered explanation of the US portrayal in world media. But of course it is only my opinions on a variety of topics. I will also use the word American in one instances to refer to the US population as that has become common in popular use despite the fact that many other countries are within the Americas and it is unfair to refer to the US solely as America. 

To begin if we examine the US media it has been shifting to more sensationalist over the past decades notably due to FOX news working essentially as a propaganda arm for the republican party. With its large viewership this generates and reinforces the ignorant views of many US citizens. Of course the other media sources (regardless of political leanings) are far from clean here as they also sensationalize stories because it is good for their bottom line. Good ol' capitalism. As such a widening gap in ideologies between our two party political system has developed. 

Now thinking about our political system, the way the US primaries work is each party has their own primary to select their candidate, this has shifted republican candidates ever farther right to appeal to the vocal radicals. Thus, resulting in giving them more media attention which grows their numbers, forces politicians to pander to them, and portrays the US as an ignorant wasteland to the rest of the world. This in connection with the fact that more moderate views are "bland" and do not drive ratings so they are not reported on leads to a disproportional portrayal of those views as inherently "American".

Now to tie in culture, the individualism of the US compared to many other cultures also plays a role here. While individualism is not inherently bad it brings about the view of one's self as a leader and not a follower. This has been capitalized on by media and politicians to convince people that they are the leaders and "not being sheep", as they would state. Despite the fact that they are blindly following the ideology given to them while thinking everyone else is being a sheep. Quick tangent here, but as Christianity is the predominant religion in the US you would think these individuals would rejoice in being sheep. The lord is their shepherd according to Psalms 23. This warped individualist view of being the leader I think pushes these individuals to be more vocal about their views compared to many with differing views who do not see themselves as in charge.

Finally the history of the US is tied in to many of these factors and forms a foundation for these events to occur. The civil war formed a huge divide between parts of the country as you would assume a civil war would do. However, with the North's victory there was not the same sort of changes you would generally consider in the aftermath of a civil war. This enabled the south to hold on to many of their ideals and propagate them. This is abundantly clear if you look at the United Daughters of the Confederacy in the early 1900's which pushed for confederate statues and modification of school curriculum within the south. This led to generations of children who never learned the true history of the civil war, racism, and slavery. Many of whom ended up idolizing the confederacy without any real understanding of what it was. These individuals then find themselves at odds with many others in the US and goaded by their media overlords want to fight for it. 

As an added thought a big part of it is the ridicule of the ignorant rednecks by some of the US media and population, including myself, which actually then portrays the US as such to the rest of the world. It likely also prompts those who are close to the redneck mold to think they should be that way and provokes those who identify with similar beliefs to become more vocal.

There is much more that can be said about the topic and many more factors that contribute but these are some of those I find to give a clear picture of why the US is seen as ignorant and idiotic by much of the world.