Right wing Democrats like Feinstein, Lieberman, Clinton, Schumer and others will support the Iran war. Kerry and a handful of others WILL oppose it. They will be attacked, with their patriotism threatened.
Thousands of Israeli civilians will be killed by rockets fired on major cities. This could reach much higher numbers if Iran uses chemical warfare weapons.
Tens of thousands of Iranian civilians will be killed in the first few days of the massive attack the US will wage upon Iran.
Within days, Iran's air power and communications will be destroyed. Power generation operations will be taken out. US losses will be far greater than those seen in Iraq. But because the war will primarily be an air war, the US will not see massive troop losses. The US Navy WILL see far worse losses than the Iraq conflict. Iran's weaponry will prove effective in attacking US naval vessels.
As with Iraq, the US will relatively quickly "win" the war. Iran will, like Iraq, fold quickly, forcing the US to manage a larger country with a much larger population. With military resources already thinly stretched, the US will bring in massive levels of privatized forces-- blackwater troops, mercenaries and oil field and pipeline security guards.
Unlike Iraq, the US will brazenly grab the oil production facilities and take them over, using expensive mercenaries to guard the oil fields and piplelines. It will not work. The Iranians will sabotage the oil wells, not permitting the US to tap their energy resources. This loss of millions of barrels a day in oil on the world market will hurt all the G8 nations and the developing nations.
Right wing talk radio and Fox News will applaud the Bush administration for its "bold" decisiveness. The men who make up the bulk of the remaining Bush base will feel more manly, vicariously experiencing the attack on Iraq as a way to personally feel more macho, more potent.
The UN, hobbled by Bush's appointee, John Bolton, will do nothing of import.
In the US and the rest of the world:
Oil prices will explode-- surpassing $100, $150, even $200 a barrell, with gas prices, jumping to as much as $10 a gallon.
Prices will go up all over the world. This will be very damaging to the USA's already falling reputation and image. In nations with weak or marginal economies, the economic impact of the energy implosion will lead to deaths by starvation and heat prostration, and riots.
The energy price explosion will have a domino effect upon the economy-- affecting all goods that must be trucked, refrigerated, that include petroleum products...
This will affect local taxes as heating, cooling, local road repair costs and more all triple in price.
Short, one or two day gasoline shortages may occur, but there will be plenty of availabiilty of gasoline. The oil companies will be sure to take advantage of the situation.
Rapture ready fundamentalist Christians drooling for the messiah to come will be even more excited, hoping that the new levels of conflict will be bringing them closer to being "raptured" up to heaven with Jesus.
As the focus is moved away from Iraq, Shiite attacks on Sunni's will increase, and Iranian operatives in Iraq will become more bold, more aggressive, killing more Iraqis and more US military personnel.