Saying that we're better than most but not as great as we could be is a cop out. The implication of your comment appears to be "let's be upset about N.K., but you're holding the U.S. to too high a standard. The institutions of the U.S. are not nearly as deserving of public outrage as those of N.K."
It's been my experience that most of the wealthy/privileged in the U.S. are simply unaware of how horrible things are[1]; that it's nicer to believe convenient fictions than be faced with a moral/emotional imperative to "do something". For these and other[2] reasons, America's institutions are more deserving than N.K.'s of American/Western public attention and outrage, proportional to the degree that they violate American values.
The implication is absolutely that the institutions of the U.S. are not nearly as deserving of public outrage as those of NK. I simply don't understand how you could come to any other conclusion. Death camps and executions for those who speak out against leaders are aren't worse than three strikes laws? Come on.
I thoroughly agree with the first sentence of your second point. I would go further to say that, since almost all of America is wealthy and privileged (compared to the rest of the world), and add in the fact that only ~22% of our citizens have passports, most of us have no fucking clue how horrible things are in much of the world. That's why I think exposing this kind of stuff, and shaming those responsible, is worthwhile.
The gains to be had in America are, relatively, minor compared to the gains that could be achieved for hundreds of millions around the world. Look at the recent events in the middle east. How much of the was precipitated by worldwide outrage over human rights issues for the last 30 years? I don't know, but I can't imagine they didn't bolster the protestors' resolve to some degree.
That's not to say we should ignore the problems here, and obviously people aren't. There's a thousand different versions of the Innocence Project run by people trying to right the perceived wrongs in all segments of American society. But there's enough outrage to spread around. To say we don't, as individuals, have the time or energy to focus a miniscule amount of attention on the worst off of those around the world is ridiculous.
You're conflating the legal system with the penal system. It's a common mistake, but the "3-strikes laws" are part of the laws and how they're enforced, which is the legal system. The penal system is about carrying out sentences and imprisonment. In some case the penal system is actually an advocate for the prisoners against the legal system. For example, prisons force law enforcement to get warrants before they'll let them listen to prisoner phone calls if they haven't been convicted yet, or sometimes just in general.
That's not to say what you mention about the legal system isn't screwed up, it's just to fix the penal system you have to focus on things the penal system can change. They can't change the 3-strikes laws, but they can change early release programs, surveillance, oversight, IT budgets, conditions, training programs, guard training, etc.
Don't get me wrong -- I'm definitely concerned about the suffering that happens in foreign countries, and I think that people should be aware of it.
Say every American was upset at N.K.'s horrible treatment of prisoners. So what? What's going to happen -- the U.S. would need to go through China before it could touch N.K. And bombing a country on humanitarian grounds is a little absurd.
But if every American were upset about the penal system, or about "3 strikes laws", or prison rape, the problem would be solved almost right away (indeed, American complacency and populism caused some of these problems in the first place).
It's been my experience that most of the wealthy/privileged in the U.S. are simply unaware of how horrible things are[1]; that it's nicer to believe convenient fictions than be faced with a moral/emotional imperative to "do something". For these and other[2] reasons, America's institutions are more deserving than N.K.'s of American/Western public attention and outrage, proportional to the degree that they violate American values.
[1] e.g. http://bit.ly/mwO0dP
[2] another important reason is that American outrage can actually do something useful in the U.S., but is almost completely impotent w.r.t. N.K.