Because the United States of America needs the approval of its people to declare war. Further, its people were thoroughly disgusted with war after The Great World War and resisted the idea of America entering another war. Thus, it took an act of aggression so agregious that the American people would set aside their pacificistic hopes and desires and agree to enter the war with full abandon.
Historically, this was accomplished by the Japanese attack on Pearl Harbor and other minor Japanese incursions on American war materials and territories. Without those incursions, America may (or may not) have stayed out of the war until too late.
Requiring a die roll for America to enter the war symbolizes the politicians of America’s need to keep their constituents happy by entering or staying out of the war. Obviously, the American people immediately demand vengeance if America is attacked, as they did after Pearl Harbor (greatest mistake in Japanese history) but the sniping of islands in the Pacific was never enough to justify America’s entrance in the war.
It seems logical, on paper, that on Round 3, collect income phase, and each subsequent round thereof until America is in the war that the player of the United States of America throws one die. If the die throw is two or less, the United States collects their war time National Objectives and may declare war on any nation thereafter. The target number is increased by 1 for each of the following events:
- Novgorod under Axis control
- Volgorod under Axis control
- Muskva under Axis control
- London under Axis control
- Any Dutch territory (except Holland) is under Axis control
- Any South American nation under Axis control
- Any Canadian territory under Axis control
America is automatically in the war if any American warship, plane, ground unit or territory is attacked.