Excellent point. 12 or 13 (depending on who is counting) allied countries provided troops, with the US, Britain, and Canada landing the most.

I will take this WWII nod to recommend a fine book that I just finished (by definition, I recommend any book I read through to the end), HITLER'S AMERICAN GAMBLE: Pearl Harbor and Germany’s March to Global War (2021), Brendan Simms & Charlie Laderman. The story of one of Hitler's major categorical errors, the other being invading Russia, but this one rather less considered.

Within days of Pearl Harbor Hitler did something he did not have to do, he declared war on the US, thereby drawing the world's greatest industrial power into a war. FDR had been unwilling to declare war on Germany because he did not think he could get a declaration through the still isolationist Congress. Japan yes; Germany, no. Hitler solved FDR's problem.

What makes HITLER'S AMERICAN GAMBLE a good read is that the essentially one week of world war history is told tik-tok style, moving around the globe -- Tokyo, Singapore, Moscow, Rome, Berlin, Honolulu, etc. -- as the events are unfolding, events that the various parties were not always aware of and certainly did not in many cases understand. A huge example, Japan did not alert the Germans it was going to attack Pearl Harbor. Hitler was, shall we say, miffed. I wonder if that annoyed him to his own declaration. One-upmanship as a strategic error.

https://www.amazon.com/Hitlers-American-Gamble-Harbor-Germanys/dp/1541619099