“Did Adolf Hitler, Mussolini, Germany and Italy really have to declare war on the USA with the news of the attack?”
The best way to answer this IMO is to listen to Hitler’s declaration of war against the United States speech with subtitles. In effect, the US was already conducting war against Germany, attacking or reporting German merchant and warship positions to Allies. So, despite Hitler’s repeated efforts before and throughout WW2, Hitler reluctantly declared war to show support of his greatest ally, Japan, but also because United States would have soon declared war on Euro-Axis and Germany had had enough of US’ underhanded ways.