WWII wasn't a world war until the United States entered the war when we declared war on Japan on Dec. 8 1941. The United States was in a state of war knowing a attack was eminent but just didn't know where the attack would come from. All patrol ships had orders to fire on any unidentified ships.
You must be joking? A) The world was at war long before Pearl Harbour.
The Battle of Britain had been waged.
Russia had been invaded
And the only battle of note on US soil was Pearl Harbour which isn't on mainland USA. Further, was there any fighting of note in the whole American continent (both north and south)? Your understanding of world is a little flawed. Either that or the rest of us are wrong.
B) What is a "State of War"? A state of war only exists after a declaration. That's why most of the world uses the term conflict after Vietnam and Korea in historically dealing with them.
C) I would suggest every patrol vessel fires on unidentified ships whether it was 1941 or 2011 if those ships pose a threat. i'm sure if I was to sail up to the CVN-77 in an unmarked boat I wouldn't get a bunch of flowers thrown at me.
Next time for Trivia maybe ask "How long is a piece of string? It's a bit more precise.