It's eight fifteen and that's the time that it's always been
We got your message on the radio
Conditions normal and you're coming home
—"Enola Gay" by OMD
There are currently 450 LGM-30G "Minuteman III" missiles buried underground and encased in tons of concrete in Montana, Wyoming, and North Dakota. Each missile is capable of carrying a warhead with a minimum blast yield of 300 kilotons (TNT equivalent, 300 thousand tons of TNT) and has a range of approximately 8,100 miles, accurate within 150 meters. As you read this, they are all fully operational, 24 hours a day, 7 days a week, 52 weeks a year...blah fucking blah.
"Little Boy," which was dropped at 8:15 a.m. JST in Hiroshima, had a maximum blast yield of only 18 kilotons (TNT equivalent, 18 thousand tons of TNT). "Fat Man," which was dropped at 11:02 a.m. JST in Nagasaki, had a blast yield of approximately 21 kilotons (TNT equivalent, 21 thousand tons of TNT). One kiloton can be expressed as a cube of TNT that is 8.46 meters on a side (27.8 feet).
I heard once while visiting the Trinity Site in New Mexico that the total blast yield of Fat Man and Little Boy (roughly 39 kilotons) was greater than all of the explosive devices used by all the armies in WWII.