The B-83 Hydrogen Bomb is the most powerful atom bomb in the US. It is small, only about 12 feet long and two tons but one of these has the force of 25 million tons of TNT. It can destroy entire regions of the earth but it is not the biggest ever made. Until 2011 the B53 was the biggest with 2X as much power but was dismantled. The Russians had the Tsar Bomba, slightly more powerful but was also dismantled. The US has about 5000 atomic weapons, down from 25,000 at the height of the cold war.