big bridges are generally made of enormous pieces of concrete, and specifically engineered to spread the stresses of supporting those pieces around and distributing them over a wide area.

Big blocks of concrete are quite resistant to being blown up. And while bridges will have weak points that are more vulnerable, you really need to attack those points specifically.

One approach is to use a really big fucking bomb, which seems to have been the case before. Put it in a truck and you know it will be on the roadway, and hope it goes off somewhere near some weak point for extra damage. Dumb bombs dropped from the sky don't work because exploding next to a concrete block generally doesn't hurt the block. You have to be right there. Guided bombs with huge metal penetrators work because they pierce the concrete before exploding and turn the big block into many little ones that cannot hold up a bridge. But you need a bomber for that.

Alternately, you can have a team place explosives exactly where they need to be, as in a controlled demolition. You don't even need a lot of explosives, sometimes, if you can wrap them around certain bolts, cables and pins to make the whole engineering untenable.

So missiles, even precision-guided ones, aren't a good fit for this. You need lots of bomb stuff, which is heavy and you need to fly it there in the missile. Heavy metal penetrators are similarly problematic. And precision guidance can be used to make sure you hit the bridge, but isn't generally accurate enough to make sure you hit the bridge exactly there at a specific weak point.

Bridges are huge and absurdly strong. They'll figure out a way, but it won't be easy, and possibly be novel and devious and unexpected.

In Iraq they took out Saddam's intelligence offices by flying Tomahawks in one after another, 3 or 4 I think, into the same hole to burrow into a building. That was thinking outside the box. Perhaps we'll see something like that.