A kilo of TNT probably has a blast radius of 10 feet or so. So we’ll make a crazy estimate and say about 200 kilos to obliterate an acre (200 feet x 200 feet and then double it to fill in the gaps) Quick google-fu says Nebraska is about 50 million acres, so 50 million times 200 kilos = 10 billion kilos. So I would put the minimum amount of TNT necessary to obliterate Nebraska at about 11 million tons.
If you want the fewest possible explosions, Tsar Bomba had a blast radius of about 25 miles. Nebraska is roughly 450 miles by 200 miles, so a very rough calculation tells me that 9x4 numbers of Tsar Bombas would be needed to obliterate Nebraska, but we’ll need to take away some for the Colorado divot and we’ll need to add some to fill in for areas between the circles, so let’s add another 50% for safety’s sake, so 941.5 = 54 Tsar Bombas to level Nebraska. A Tsar Bomba had the equivalent of 50 megatons of TNT so the equivalent of 55 million tons of TNT * 54 = 2.97 billion tons of TNT.
So, you could save yourself a lot of money by lots of little explosions rather than a few big ones.
