Four Days in December 1941

This is a post that has nothing to do with law. On December 7, 1941, Pearl Harbor was attacked. Four days later, Hitler declared war on the United States. What happened during those four days between the United States and Germany?

What I mean by that is suppose Hitler had not declared war on us. Were we going to? Was that uncertain? What were those conversations like? Perhaps there is a history of World War II that discusses this. If so, I'd be interested to know. If not, I think that this topic could make a great book. 

UPDATE: John Lucks wrote a great book called Five Days in London: May 1940 that did something similar for Winston Churchill's start as Prime Minister.