One incident would definitely be during the cold war more specifically during The Bay Of Pigs
another would be during a false alarm in which we thought Russia had fired nuclear weapons at us and refrained from firing back before being sure
B) They had a complex civilization that was destroyed by the Spanish conquerors.
By the time of the Spanish invasion, the Aztecs had devloped a strong civilizations, they had a system of trade & commerce and were quite wealthy. They also had a primitive form of "police" and a banking system.
It increased the size of the United States because it was based on the idea that America was destined by God to expand from the Atlantic to the Pacific, in other words, it encouraged many to expand west.
hope this helps i actually just learned about this in class :)
B) Conquer new territory in Africa and Asia.
