When America got the bomb they used it as a terror tactic "We will kill as many of your civilians as we can unless you do what we want."
Which conveniently ignores the connection between civilians and the military in an industrialized nation-stated involved in total war against another industrialized nation-state. Namely, this simple formula: no civilians, no economy; no economy, no military; no military, no war.
The tanks, planes, ships, guns, bullets, shells, radios, uniforms, and much more, are created by the civilian workforce. The raw resources needed for that military production is gathered by the civilian workforce. The soldiers, sailors, and airmen are drawn from the civilian workforce. The energy needed to power the factories as well as the machines of war is produced by the civilian workforce. And so on.
In Japan's case, due to its production often being dispersed, this meant have to raze much of a city in order to hit the military hardware and vital subcomponent production.
Germany bombed cities, but whether through lack of opportunity/capacity or ethics or strategy never attempted to level cities the way that Bomber Command did.
Yes, it did. The Blitz was precisely an attempt to level London. The problem for Germany was that it never developed an air force capable of doing the job—strategic bombing was a low priority. Germany's bombers were virtually all twin-engined types intended for the tactical role of supporting the army. And to conduct a strategic bombing campaign effectively you need a lot of four-engined heavy bombers—something which Germany never did.
As for "levelling cities the way Bomber Command did" this ignores the many real—if indirect—effects on the German war economy Bomber Command's effort had. Moreover, the Battle of the Ruhr (March to July, 1943), as Adam Tooze lays out convincingly in his book
The Wages of Destruction using German records from the time, had a profound effect on German war production. The armaments "miracle" that Albert Speer had put together was stopped in its tracks. The RAF was within reach of achieving a significant victory—only it ceased the campaign against the Ruhr (for several reasons) and switched focus onto Berlin.