Stop trying to excuse your beloved 'merika. Nobody even mentioned who was aligned with whom only that Japan was backing a corner by the yanks which led to Japan entering the war. So what if they were at war with China at the time? That also is not relevant to the point at hand. And don't even start about how without American finances, factories and encouragement then Hitler's Germany wouldn't have even gotten off the ground. Also, without the attack on Pearl Harbour, Hitler would not have (probably) declared war on the yanks either. https://en.wikipedia.org/wiki/German_declaration_of_war_against_the_United_States
It's not as simple as we were led to believe growing up.
