Give the large amounts of sugar and other goods brought to New England through triangle trade, North America would have benefited most. The Caribbean received manpower in the form of slaves from Africa, while Africa sold its mapower in exchange for goods (lots of rum), meaning it most likely benefited the least.
Hitler's power was not checked when the US entered the war. The war with the US was between them and Japan. The USSR did join sides with the allies when Germany broke an treaty. However, the US did win the war between Japan.
