They wouldn't mention them much in general books or curriculums basically because of what United said: they rarely or never saw action. They had been creations, some tested, some not. So, good thing we invaded Germany when we did or he could have used em effectively. German's also gave their prints for the ME-262 (I think it was just the engine layout, not the whole plane) I believe to the Japanese. I think we sank one of their seacraft that held the info on their way back to Japan, but another one still got there. Like Germany, the Japanese never got to use them because it was too late, but they did start to produce them. Edit: I believe the Japanese did use a couple jet engine aircraft, but there sure were not many of them. Could these "secret weapons" have made a difference in the war? Can't really tell... But they did have the technology and were already starting to build models and models of jet planes.