Why did the allies lost from battle to battle during ww2 before midway?

In Europe the Germans just had far superior tactics to the allies, even they were surprised by how quick and totally they defeat the allies on the western front in 1940 and didn't have any plan to follow up on Dunkirk and the fall of France. In the pacific the US was totally caught off guard and joined the war with a good deal of the pacific fleet smoldering in Pearl Harbor.