I think it would be unwise to swing from one extreme to another when talking about this, especially with only anecdotal evidence. Yeah, there were a lot of people helping each other, as is often the case in disasters. But shit was messed up. Nothing against the city, I had (past tense, pre-Katrina) friends there and I love it, but it could be a downright scary place.
Mark nailed one of the big points: the situation got worse as the ineptitude of the government on the city, state, and federal level screwed them even harder than they were screwed initially. Can you even fathom that level of frustration?
I think disparity is a huge part of what contributed to the issues as well. Firstly, some of the worst-off areas of NOLA and around were hit hardest by the levee breaking. In a city with some pretty bad disparity already, emphasized by the fact that we’re supposed to be the best-off country in the world, really ratcheted up the problems.
An offshoot of that is that some of the worst things we heard about, like the situation in the Superdome, came from shoving these disparate elements (haves, have-nots, have-even-lesses) together in an anarchic environment when they previously never mixed. That was further exacerbated when people were dumped in other cities like Houston.
Mark’s second point is equally valid — I’m not enough of a weeaboo to imagine I know what Japan’s culture is like on any deep level, but I can say this with some confidence: Japan is more culturally homogenous than New Orleans, so the racial/cultural problems would be less of an issue.
So to sum up this mess of a comment: The problems stemmed more from (lack of) government response, economic and racial disparity, and the link between those (i.e., black = poor to a large degree) than from the disaster situation itself, but the problems were real. And I think those factors would be less significant in a TM8.0 situation than a Katrina situation.