Increasing economic turmoil as the rich get richer, the poor get poorer, and the middle class disappears. Then, as oil supplies get really low and prices on everything (and I mean everything, oil isn't just for making gas for your car) go up, and the already poor majority of the American populace will hopefully realise their predicament, and rise up against the government, overthrow it, and replace it with one that either goes back to actually following the constitution, or one that is a total overhaul.

Either that, or we end up destroying ourselves and everybody else in a nuclear war with China and/or N. Korea.