Andy -- The real issue is not so much that Americans are stupid (most of us are, but that's not the issue... most people anywhere are stupid, but as a species we blunder along anyway) but that we're so damned pig-ignorant. Most assume that it's only those assholes on the Other political Side that are ignorant, but in fact only a tiny minority of the U.S. population has a clue, period. The root causes are controversial and go back at least 2 or 3 generations at this point, but everybody on all sides of the various chasms that divide American politics seems to agree that education (and child-rearing in general) in this country is generally awful and getting worse, and that the only people who reach adulthood as fully well-informed and rational beings are primarily auto-didacts who had exceptional parents.
In its youth the Internet mitigated ignorance by making it easy to interact with strangers far away whose points of view might possibly differ, but is now mature enough that it's possible for anyone to barricade their minds against conflicting opinions by only visiting web sites, reading blogs, watching commentators, etc., that they already agree with. (That was the default condition back in pre-telecommunications days, where you either toed the local party line to survive among your neighbors or you hightailed it for somewhere else where the dominant prejudices were closer to your own.) Most politically-motivated people, if they seek out conflicting points of view at all, do so to stir up their blood at the hateful smears, outrageous falsehoods, faulty logic, and outright stupidity exhibited by Those Guys Over There. (That's why I read sites like LifeSiteNews and OneNewsNow.)
In such an environment, when you then touch on an issue that's highly emotionally charged, both sides get defensive, start spouting the same dog-whistle slogans they use in their own enclaves to demonstrate how much they agree with their fellows, and wonder why those assholes on the other side just don't fucking get it. Because we're out of the habit of actually communicating with someone with a differing point of view, we rattle off a shorthand response that makes perfect sense to anyone on our side who's already drunk the Kool-Aid (they actually used Flavor-Aid at Jonestown, but let that pass) but to outsiders just sounds like thought-stoppage (which it largely is). Insistence is substituted for argument.
What Anton has alluded to but not unpacked for you is that, as the saying goes, "Political power grows out of the barrel of a gun." (I'll leave it to you to look up which right-wing red-blooded true-blue American gun-crazed Red-baiting John Bircher originated that phrase.) Laws are backed up by the threat of physical force (that's why we call it law en-force-ment), which, at root, means guns. Even laws against the spread of guns are enforced, ultimately, by men with guns. If the government eschews guns, eventually someone with guns becomes the government. because murderers tend to outlive their victims. If, on the other hand, the government does remain armed, then some of those firearms will be diverted to people who are not legally allowed to have them. This is the tautology behind that other shorthand phrase so often cited but so rarely explained, "When guns are outlawed, only outlaws will have guns." (You never hear it stated as "only outlaws and the government will have guns". The government having guns is just assumed... again, by both sides.)
As Canada and a few other civilized countries demonstrate, widespread gun ownership and a low rate of gun homicide are not mutually exclusive. The discriminating factor is culture; Canadians, as a nation, are less likely than Americans to use their guns to blow holes in other people. Maybe they interact with people whose opinions differ by trying to communicate and not just by lobbing slogans at each other.