the last thing I heard, or read, about the MN bridge collapse was that it may have been caused by a design flaw, not wear and tear; so, if you were going to blame a president it would have to be LBJ, but at least you could still get away with blaming a war, Viet Nam.
No design is perfect, and some flaws in this design must have been known back then, as the standards for bridges changed shortly after it was built. The fact that they don't make them like this anymore should have told the MNDOT that this bridge needed a more vigorous inspection regime than newer bridges. If the know flaws of this design included total collapse due to unpredictable single part failure, then replacement should have been scheduled.
It's not like the bridge got a 100% rating at the last review. Then you could blame somebody in the LBJ era.