[justa-hairyape]

a) Not getting involved in a stupid EUropean quarrel between Britain, France and Germany and letting them settle it themselves until the Japanese bombed Pearl Harbor.

If the US did not get involved, Germany would have had a few more years to develop the A-Bomb.

[.cnI redruM]

Exactly what we did. The German A-Bomb is exactly what would have resulted sans the Japanese attack on Pearl Harbor.