The US dropped "the mother of all bombs" on Afghanistan

The United States first used conventional weapon in Afghanistan, comparable in power to nuclear one. "Mother of all bombs" as it was affectionately christened in the Pentagon, was used in the province of Nangarhar against militants of the "Islamic State". The first combat use of bomb of this type can be considered a kind of test. Commenting on the bombing, White House spokesman Shaun Spicer did not answer the question whether they would be applied in Syria or against the DPRK.
GBU-43B - was first tested in 2003. But until today it has not been used in combat conditions. The explosive power of such a bomb is 11 tons in TNT equivalent.

However, this is not the most powerful conventional weapon. The Aviation Vacuum Bomb of Advanced Capacity (AVBPM), created in 2007 in Russia, exceeds the American analogue of destructive force by 4 times.