The U.S. doesn't have rights to the Strait, so I don't see how it would be a direct declaration of war against the U.S. to block it. Obviously it would affect our oil economy, but in terms of legal provisions, the Strait is not ours so all of this entitlement to attack Iran about it is uncalled for. If the U.S. attacks Iran over the Strait then we would be violating international law. Despite what the warhawks would have us believe, we can't just go to war with any country we want. Mind you, the UN law has been flouted many times in recent years by several of the big powers, so it might not matter, especially if the U.S. forms a coalition again.
I have to agree though that during a recession and an election year, another major war would be extremely unpopular - but it could happen anyway, since oil industry is our biggest sacred cow. Anything that obstructs it would suffer the rath of the Republocrats. Not to mention, the POTUS has the unilateral power to deploy the military now, so it would actually be up to King Obama and not so much our Congress, unless the GOP makes a push for it to happen.
The only loose canon here is Israel, and their government has been looking for any excuse to bomb the **** out of Iran for several years now. The tensions are climbing. It wouldn't be so severe if Iran weren't already surrounded by nations that have been infiltrated by our military. They are likely to be more nervous, and more nervous means they will take measures to procure their security.