It may not make for a very good movie, but our military is probably better prepared for a giant monster attack than you would at first think. I once ran the numbers on one of those penetrating bombs and, if the aero calculations were correct, when dropped from about 60,000 feet it hits the ground at well over Mach 2. Yeah, I think that a ton of explosives moving twice the speed of sound would take one of these things down quite nicely.