Quite interesting...
But citing WWII as an example, wouldn't that be an exception to the rule? The reason we won the war was because we (they) all pitched in to the war effort.
Americans were terrified. It was an existential crisis. So was the Great Depression. Those events happen very rarely. America was not united during the American Revolution or the Civil War obviously. There may be unity again, but it will take an existential crisis to make it happen.
That's my point. It shouldn't take fear or terror to unite us. We don't need a crisis to be united.
Unfortunately..I think that is exactly what must happen before anyone forgets boxes and labels and become just AMERICANS.