Not sure where you are going with that post. To continue with the juxtapositions, for Germany and the USA the declarations of war were reversed from 1917 to 1941.
My point was that the French had publicly and repeatedly declared their support of Poland. But on September 1, 1939, when Poland had clearly been massively attacked, what should have been an automatic declaration by the French government was instead a prevarication. You cannot be a “little bit at war” any more than you can be a “little bit pregnant.” Either you are at war or you are not. As will become quite evident, the French never really considered themselves to be at war with the Germans because from the outset they really didn’t want to be.
Certainly not to disagree with you. Just to point out that where Declarations of War had previously been considered diplomatic necessities, by 1939 it was apparently strictly optional, and often not so desireable, and sometimes didn't even mean real war -- as your example of the French demonstrates.
Even Roosevelt in 1941 did not ask for a straightforward "Declaration of War" on Japan, but instead the rather curious turn of phrase he asked for was: Congress to declare "that since the...attack... a state of war has existed."
I conclude, the declarations themselves, when they even happened were meaningless, and that may explain why we've seen none since?