@mitch the "established history" is that the US treated Japan and Germany pretty much equally, despite the difference in *race*, until the difference in *actions* when Japan attacked Pearl Harbour and (belatedly) declared war. The US gave economic support to their opponents China (Import-Export Bank) and Britain (Lend-Lease Act) to buy American materiel, but military involvement was comparatively limited in both theatres, despite a substantially greater contemporary awareness of the Japanese atrocities at Nanking than the German ones in Poland et al.

There are a number of things one can point to as evidence of racism in America at that point in history, but her entry into WWII really isn't one of them. In fact, one can look back a generation earlier to see that when Germany gave a similar casus belli in the sinking of the Lusitania, the country was certainly willing to go to war against a white enemy if that's who attacked.

I'm not going to question your experience in your family, but I'm reasonably convinced that it doesn't extend to "Usonia, in general" as strongly as your initial post suggests.