Question

How did the relationship between Japan and the United States become strained leading up to the attack on Pearl Harbor?

Answer 1

The U.S. Was Trying to Stop Japan's Global Expansion
In light of such atrocities, the United States began passing economic sanctions against Japan, including trade embargoes on aircraft exports, oil and scrap metal, among other key goods, and gave economic support to Guomindang forces.

Answer 2

It was bad. the Japanese wanted to attack american fleets.