Oooo goody, a nice thread!
First, Pearl Harbor: There are multiple views on this. The US embargo on oil had created a situation where Japan had to either surrender nearly all of their empire as untenable or invade sources of oil in the south pacific, which would provoke war with Australia & the US. Invading the US was never a viable option (no Japanese invasion was ever assembled, or ever close to being assembled), they simply wanted to destroy the US naval domination of the region. So...our armament situation had as much to do with it as our bubblegum production. On the other hand, they DID invade parts of Alaska...where the oil is...but Midway made that untenable, as their supplies would be vulnerable.
Second: Democracies dont' have a great track record for defending civil liberties. The Athenian democracy had more slaves than citizens. Robespierre's cry of "Let Terror be the order of the day!" was spoken and heartily endorsed in the midst of a fully elected ruling body. Hitler was elected democratically, and the Nazi party had the largest vote in public elections. British democracy has been...rather brutal: the only period when Parlaiment ruled without a monarch was among it's bloodiest. See Irish history to find how well their rights were protected democratically. And calling American democracy a defender of rights is hard to stomach: slavery was a VERY democratic institution (as in, the majority of Americans supported it, even at the start of the Civil War). So were the Jim Crow laws, Red Scares/McCarthyism, Veitnam drafts, Japanese internment camps, and the Patriot Act. So no, we don't have to fear a mass extermination, but claiming democracy keeps us safe is hard to swallow: democracy is by definition the will of the majority over that of the minority. And finally...keep in mind that America gained its independence by force of arms and very horrible bloodshed (only the Civil War saw a greater percentage of Americans killed) against what was then the most democratic country in the world.
As for fearing our governments, part of the reason we don't is that we don't HAVE to. We don't just have ideals, we have ways to enforce those ideals. The automatic response to such a thought as mass extermination in the US is "That would never happen; they wouldn't get away with it, people wouldn't stand for it." Well...who would make sure they wouldn't? Who would stand? Yes, there would be repurcussions, and knowing that eliminates the need for any repurcussions.