Minneapolis Bridge collapse... Conspiracy?

Obviously with Bush downplaying the strength and abilities of Al Qaeda right now, a terrorist attack on American soil would not be preferential to the Republican party as it would mean that their efforts and the sacrifice of many American soldiers has been completely ineffectual and just a waste of precious American lives and money. If a terrorist act were to occur right now it would not be in the best interest of Republicans to let it be known. That said, couldn't a few well placed small explosives take down a bridge, especially one that is positioned, not only on a major route, but that has also been rated 4 out of 10 by inspectors as far as it's condition is concerned. To me it seems that if terrorists were looking for an easy target that could not only create fear, but also be devastating in sense of American infrastructure and transportation, that this is as good a target as any! Why is there no mention of the possibility of terrorism? Republican cover-up?