What is a nation-state?

What would lead a historian to consider two events to have a relationship of correlation rather than causation

In japan, the had nearly total power, but he was also assisted by

By the late 1930s, how were u.s. officials beginning to view japanese policies of expansion? a. they attempted to join forces with japan so as to increase u.s. territory. b. they warned them to stop expansionist actions or face potential u.s. intervention. c. they sent representatives to japan to work out territorial rights in a diplomatic fashion. d. they became fearful of their military power