I would disagree. This sentence is about the Unites States, not Japan, and the use of passive voice reflects that.
This is disingenuous. Removing the bad actor in this sentence removed part of the cause for the effect. Not an attack happened, a japanese attack happened.
I you feel that the actor is an important part of the sentence, you can include it in passive voice as well: “However, it was attacked at Pearl Harbor by Japan, and then chose to enter the war.”