In the view of the diaries and memoirs of most German generals, the military command was completely horrified at the time Hitler declared war on the Americans in the year 1941. Further, the German staffers did not actually consider all the types of invasion of the United States of America since approximately 1910. Moreover, in the early months of 1942, the German war staffers factually had a discussion in Berlin on whether they had any chance of attacking the US or not. At that time, they had two main ideologies, which contained the only chances of hope of any sort of success in the war. The first concept was to effectively occupy Iceland as well as Greenland, build up bomber bases, and continue to bomb the east coast of the US. According to this idea, the Germans were to bomb the US east coast so that the deference of the US could be eradicated and allow for the invasion force to move in.
On the other hand, the other idea was to set up a base for the Germany Navy in the Caribbean, mostly in Puerto Rico or Cuba, and use the base as the staging ground for the attack on the belly of the United States through Texas-Mississippi and Florida Gulf shore. Therefore, for the two plans to succeed, Germany had to have undoubted control of the sea lanes. Hence, the war planners turned to the German Navy and particularly the U-boats, which was hoped would decimate the American naval ability in the Atlantic. It is important to note, however, that there was no combined strategy between the Army and the Navy. In the Nazi way of doing things, the various services actually had little to do with each other, and this led to the Army war planners literally sitting back and waiting to see what the Navy would do. In the end, the U-boat attacks on America were highly successful but nowhere near what would be needed to start establishing German bases in the western hemisphere.
By the summer of 1942, most of the German staffers agreed that attacking the United States wasn’t going to work. As a last-ditch effort, it was suggested that maybe if Japan could score a tremendous victory in the Pacific, occupy Hawaii, and attack California, then American resources would shift to the Pacific theatre, leaving the East Coast open for an invasion. The Germans also had a few ideas regarding putting agents behind enemy lines, creating “fifth column” movements, and attacking the U.S. from within.
In the end, Japan’s devastating defeat at the Battle of Midway made a Pacific victory impossible. The only attempt at putting German agents ashore in the U.S. (Operation Pastorius) met with absolute failure. Hitler himself also didn’t help the matter, in that he had little interest in America, refused to even discuss American strategic capability with his senior commanders, and thought that the country was run by Jews and minorities with no fighting spirit and thus the United States wasn’t really a threat. As we know today, Hitler was wrong.