Relations with Germany were already pretty sour prior to Pearl Harbor. Submarine warfare in the Atlantic and Germany’s aggression were obviously damaging U.S.-German relations. So was the U.S. curbing Nazi activities at home through the Smith Act and the Dies Committee (you might know it from a different name: HUAC).
There was hostile action from the Germans (as well as the Japanese) against the United States (and vice versa) prior to Pearl Harbor.
https://en.wikipedia.org/wiki/First_engagement_of_neutral_United_States_in_World_War_II_before_the_attack_on_Pearl_Harbor
I posted an article about one of those incidents months ago.