sphinx paraphrasing Churchill:
"Three times in the past hundred years, the streets of Paris had trembled beneath German boots, and echoed to the thunder of German guns." As you said, the exact quote would be worth studying.
German troops did parade though Paris in 1871, but not in the First World War, ever.
And it's hard to imagine Churchill referring here to Napoleonic wars when the Prussians & Brits were allied!
But we can make your paraphrase of Churchill accurate simply by changing the word "and" to "or".
Then it could simply refer to the First World War, as you noted, in 1914 and 1918.
In 1812 the French were unquestionably the Big Dogs in Europe and by 1942 had been unquestionably replaced by Germans.
Between those dates the issue was not fully settled, and German aggression was met with stiff French resistance:
Napoleon's Empire, 1812:
Germans parade in Paris, 1871:
Hitler's Empire, 1942:
I will try to find the exact quote when I rediscover my copy of the book, but ... Churchill was writing his history of WWII in the late 1940's and early 1950's. The relevant discussion had to do with the breaking of French will in WWI and the demoralization of France during the 1930's and the buildup to WWII, so the 1940 campaign does not count. To catch is point, we must look backwards from 1918. And he framed the observation in terms of three times in the preceding century. In that context, I think he must have been reaching back to 1814/15. But again, the exact quote would be useful.
In any event, Churchill's point at hand was not German aggression; it was Germany defeating France repeatedly, and the French becoming defeatist as a result. How assess war guilt in 1870 and 1914 is open to debate. In 1814/15, the French were the bad guys. France was the earliest unified, modern nation state in Europe and, for most of the early modern period, the largest nation state west of Russia. It is not surprising that France was in the habit of throwing its weight around, and France had to lose a couple of wars to realize that a unified Germany totally changed the game.