I’ve just finished Empire by Orson Scott Card, most well known for the Ender’s Game series. This novel is about a very near future civil war in the United States, and he lays out a plausible scenerio of how this might happen.
In the book, it occurs just within the U.S., but he has also written a very interesting post describing a more likely scenerio describing how our civilization could fall. I considered posting some snippets, but you really have to read the whole thing. He lays out some necessary background before getting to his main point that is important. My only criticism of his logic is that I believe we would use military force in a WWII, no-holds-barred way before we let it get to his predicted end, but even that might be too little too late.