I realize Hitler not declaring war on the US has been discussed before, with the conclusion being that an incident related to the Battle of the Atlantic would probably have drawn America into the war against Germany within a few months anyway. But what if, in addition not DOWing, Hitler had also, to avoid such an incident, called off all U-boat operations and cancelled the submarine building program, with all its resources redirected to production for the ground war against the Soviet Union? How long could the United States have been kept out of the war with such a course of action? What would the effect on the Eastern Front be?