Adolf Hitler, like another racist madman of a later era, Osama Bin Laden, hated New York City as the symbol of all that was good, progressive, and great about America. (Both of them also hated New York for its vibrant, vital Jewish community.)
After the United States began daylight bombing raids over Germany in 1943, Hitler's Gothamophobia grew to insane proportions. Unfortunately for Der Fuhrer, America was protected by a mighty moat---The vast Atlantic Ocean on one side and the even vaster Pacific on the other. Although Charles Lindbergh, Wrong Way Corrigan and Amelia Earhart had all proven that the Atlantic moat could be crossed in a single hop, the warplanes of the era simply did not have the fuel capacity or the payload capability of reaching American shores, mounting an attack, and returning home.
Too late in the war, Hitler ordered Hermann Goering's Luftwaffe to design and build "Amerika Bombers" that could make the 7,300 mile round-trip. The Me 261 was ramped up into the Me 264, a four-engine high-capacity bomber theoretically capable of reaching New York City. However, only one prototype was built, and it proved too costly to operate. By late 1944, Germany simply did not have the natural resources or physical plant to produce such a long-range bomber. The 264 was also incapable of carrying more than a moderate conventional bomb load, meaning that even if the "Amerika Bomber" flew in large numbers it could not have delivered a blow worth its own cost. Without an atomic bomb to drop, the plane was useless.
Dr. Eugen Sanger, a V-2 scientist at Peenemunde, however, had a different plan --- a suborbital space plane that he named Der Silbervogel (The Silverbird), designed to fly in space carrying an atomic device. Tests with mock-ups demonstrated that although the fuselage design was flawless for its purpose, the craft's outer skin reached the melting point during atmospheric reentry. Metallurgists were unable to perfect an alloy that was sufficiently heat-resistant, and the project never addressed alternative reentry systems. Again, by late 1944, Germany simply did not have the natural resources or physical plant to produce such a revolutionary craft. Nor did it have an atomic bomb to deliver.
But these were not just thought experiments. After the war's end, files were found in Goering's office detailing a nuclear attack on New York, and a map, marked with blast-effect radii, showed that the Nazi "Ground Zero" was to have been The Bowery.