Actually, it's worse than the numbers. During WWII, before the invention of microchips, bombs were highly inaccurate and missed their targets more often than not. That could make things worse in a populated area but there are many stories of bridges, say, that needed to be bombed over and over again in order to actually hit them.
By Vietnam, the trajectory of bombs was extremely accurate, so the disparity is a little deceiving in that the bombing there caused far greater damage than the numbers comparison indicates. The bombs didn't miss their targets at nearly the rate they did in WWII.
Even if the numbers make it seem larger than they are, that's a heck of a lot of bombs to drop on a country that didn't do anything to us.
