The tunnels are the biggest part of this war.
Yes, and the US determined in post-Vietnam wars that climbing into them isn't the way to go. We blow them to hell with bombs so big we call them The Mother Of All Bombs. And we also understand that civilians will die when we engage in urban warfare, especially when there are tunnels involved.
The difference is, we're under a different kind of pressure, domestically. In Vietnam, we wanted to get out ASAP and get our boys home. While some people here cared about the civilians, too, the pressure was for disengagement on our part. With Israel, the risk factors and pressures are very different, and we can afford to be more dovish.