actually i see the US pre-emting a nuclear war.  bringing the pain to iran and the middle east.  Cheney has already said that if a terrorists attack on american soil again, the US will preemtively nuke iran.  it will either put the fear of god in everyone else because america has gone mad or it will trigger nuclear war when people start nuking all of US's allies, i.e. china nukes japan, NK nukes SK, Russia nukes the EU, iran and israel nukes each other.
That's what is most dangerous about an attack on Iran by the neocons. They know that because PO (no spare capacity left) an attack against Iran would mean worldwide recession (if not worse), so the only way to avoid it (and a war scalation) is to end it quickly. So they might actually use nukes!. Of course they wouldn't nuke Teheran, but would put to use those "harmless" tactical nuclear bombs and nuclear bunker-busters.

But THAT would be the greatest challenge we face. Because once  you assume that nukes, no matter how "small", are an acceptable way of waging war, there is no saying what will happen.

Let's hope that two catastrophic hurricanes make it impossible  to start more invasions.