What a magical world Wikipedia is*. Yesterday's post about the Nazi B-17 led to a German bomber which may have made a test flight to New York City.
Hermann Göring knew in the 1930s that the Luftwaffe might come into conflict with the United States, and this would require a very long range bomber. He proposed, and Hitler approved, the Amerika project to develop such an airframe. Ultimately, a handful of Junkers Ju 390 bomber prototypes were built.
This was a much bigger challenge that the US faced with its B-17, or even the longer range B-24. Neither of those were designed to make the Gandar-Berlin run. Even the B-29 wasn't up for this, even as advanced as it was. It took until 1949 and the B-36 before a bomber with true Intercontinental (10,000+ mile range) capability.
And the US had all sorts of experience designing long range aircraft. The Germans didn't, although this seems to have been a credible effort. The Ju 390 had a nominal range of 6,000 miles, much better than either the B-17 and B-24, or even the B-29.
The difference is that the Ju 390 was only one of many German "vanity" projects: ingenious ideas that were well executed in prototype form, but never seeing mass production. By contrast, the US made 12,000 B-17s, 18,000 B-24s, and almost 4000 B-29s. The Germans built a thousand times fewer of their big bombers.
Ultimately, it's a good thing that Albert Speer never was able to shut down all of the distracting experimental programs. Had he been able to do so, and focus on large quantities of fewer designs (Panther Tanks, FW-190 fighters, etc), it's likely that the war would have been even longer and more costly.
* A maze of twisty passages, all alike and yet all different.