A 17.5 ton bomb would devastate a city....
Maybe a very small one. In general damage radius goes as the square or cube root of the "power" of the bomb. a 17.5 ton bomb would thus have between 2.6 and 4.2 times the blast radius of a 2000 pound aerial bomb. Not something you want going off next door, or even on the next block, but not enough to devastate a city. Actually the comparison isn't quite apt, as a 2000 pound bomb doesn't have 2000 pounds of explosive, but a 17.5 ton bomb wouldn't have the same characteristics either.
They'd probably cause more damage if they broke the load up into a dozen or two smaller "packages".