German and Japanese aggression deeply affected the United States' economy and relationship with foreign powers. The growing militarization of Germany led to a reduction in trade and financial relations between the United States and many European nations, but also increased weapons trade between America and Great Britain and France. The presence of German u-boats in the Atlantic also greatly impeded American trade and led to the sinking of numerous civilian and merchant ships.
Japanese aggression was similar in that their occupation of many pacific islands and Asian territories reduced American influence within the region and their trade ties with many nations.