Reddit reviews Twelve Desperate Miles: The Epic World War II Voyage of the SS Contessa

I garnered some insight into this from the book Twelve Desperate Miles, about the SS Contessa, a banana boat that was drafted into the USA's initial charge into North Africa, author Tim Brady spends some time discussing why the USA was going into North Africa in the first place, rather than a direct charge into Europe, and disagreement with Britain about how the war would be waged was a big part of that reason.

On top of that, the book describes in detail the initial Vichy France military members who were defeated. There was some doubt as to whether or not the military would remain loyal to Vichy France, or if they would choose to fight. It seems there was good reason for doubt, as the captured military forces themselves were split; some choosing to continue to fight, others choosing to switch sides.

The phrase "unnecessary costs" that you use assumes a certain point of view, that all of the Allies had the exact same goals when, as always has been and always shall be, they each had different goals, things they wanted from the defeat of Germany, and old rivalries to boot. Prior to WW2, Americans saw the English as stuffy and foppish; however, during the war, American correspondents reporting from England as the Blitz happened (see also Cronkite's War exposed Americans to an entirely different side of the English, the stout-hearted, "stiff-upper-lip during rough times" image.