There is no war in Iraq. There's an insurgency, and yeah, if we're there another 25 years blowing them away, we might lose as many people as we did in the last real war (the Vietnam War). Wars are fought between armies. The insurgents have no army, just some poorly equipped, poorly organized gangs.

If we fight Iran, THAT could turn into a war. They are far better equipped than any insurgency, and while we would certainly win, it would not be nearly as easy as wiping out Saddam's army was. It would be easier than winning a war with North Korea though (and if we went to war with North Korea, we'd win there too, eventually). Going to war with Iran wouldn't be as rough as people might lead you to believe though, because we've got nearly 200,000 soldiers right next door doing little except playing as uniformed cops. We'd have air superiority within a day, and air supremacy within a week if we decided to tackle Iran militarily. And once you have air supremacy, everything gets a whole lot easier. Then it's just a matter of bombing targets until the enemy capitulates or there is no more enemy, whichever they choose. And then the aftermath: fighting another insurgency, assuming they capitulate before everyone is dead.