Why did Roosevelt resume relations with Japan?

Roosevelt resume relations with Japan to prevent America out of the future wars and more is discussed below in details.

Explanation:

To keep America out of future wars, congress passed a sequence of laws and Acts beginning in 1935 with the Neutrality Acts.

These acts banned firearms trades or loans to nations at war or in a civil war.

Roosevelt does not want Europeans to control the world economy and politics.

Roosevelt negotiates the Treaty of Portsmouth: In which Japan gets Manchuria and Korea, United States and Japan continued diplomatic talks and pledge to respect each other's possessions.