Ordinarily I believe the U.S. would have demanded a cease-fire. The problem is the act that triggered this conflict, namely Hezbollah killing 8 soldiers and kidnapping 2 of them. As for the "bunker buster" bombs being sent to Israel, they are designed for exactly this kind of warfare, with tunnels and underground bunkers. Hezbollah is also an enemy of the United States, let us not forget that fact.
It is obvious that civilians are suffering the most, and that Israel has been less than precise with its air campaign, and that Hezbollah has been less than concerned about the people they hide among. I know it makes sense to call for an immediate cease-fire when you take into account the loss of innocent life in this war. The problem is the future. Hezbollah cannot be destroyed entirely, that would be like canceling Star Trek...the body may be gone but a new generation of nerds will never let it die...okay, bad analogy. However, Israel has put itself between a rock and a hard place. If they stop the offensive and return to Israel, then Hezbollah will declare victory and use the "tail between the legs". That isn't going to end the conflict, only ensure that it will start all over again. Only option now is an international peace-keeping force, with no Americans, that will actively disrupt Hezbollah's hold on southern Lebanon. No good answers.