I've been predicting it for a while. My first clue: slow, surly service at McDonalds.
The real end: Katrina. Not the storm, the dissonance between our mythic power to overcome all disasters and what we actually did. In the American myth, which I believed as much as anybody, New Orleans might have suffered a setback, many people might have died, but within a few months, a year at the outside, there would be a need to put up memorials to remind people that something bad had happened. Old locals would know that it wasn't exactly as it used to be, but newcomers would have to read the historical markers to distinguish between the restored and the rebuilt.
Mythic collapse is the failure of the stories we tell ourselves that make us who we are. I'm not just talking about mytho-poetics here, although those are vital. There are harder and less pretty myths, like cash (what is unbacked currency?) and credit and the ideas that make technologies work. And constitutions, chains of command, etc. It is all story at heart. And it makes us who we are and gives us meaning and value.
I'm pretty sure that's what happened to the Maya - the story stopped making sense. Remember, they still exist, they just stopped being a major civilization and turned into a bunch of farmers. I know that's what happened to the USSR. Back in the early 1990s, it became obvious that it wasn't the Worker's Paradise and wasn't moving that way and the evil capitalists were actually doing a lot better at providing all the stuff Marx promised. The story stopped compelling, stopped making them who they were, stopped providing meaning. The little story, the ruble, had stopped providing meaning and value a lot earlier.
When the myth holds, the nation/culture does too. It is very, very hard to kill a nation/culture when the mythology is strong. You pretty much have to wipe it out to the last individual. But when the myth fails, the rest just melts away.
I think we are pretty close to that here.
But I don't see the USA breaking up like the USSR. The states LIKE being part of the US. Even in Palin's "pro-America" states, cessesionist movements have no traction. The USSR was held together by force. I have no idea what the wreckage will look like. But I think Obama will be it's first leader, which is pretty much the only bright spot.