New york daily news ,on the declaration of war over Poland. 

1 st day of world war 2 

Polish invasion, daily news 1939 

Not David Low's wittiest political cartoon - but still, a contribution to a major British "persuasion" campaign aimed at persuading Americans that entering the war would be in their interest.  As far as I can make out, this dates from July, 1940.  Americans took some persuading - one can hardly blame them.  While the "persuasion" process continued, President Roosevelt's government made increasingly effective (if admirably self-interested) efforts to support isolated Britain in resisting the Axis.  In the end, it was "semi-detached" events involving Japan's attack on Pearl Harbour, that brought the US fully into the war.  Best regards, JR.