french situation in Sedan was rather similar to what Israel faced in october 1973, Ie after an initial surprise attack the army was now outnumbered and mauled.
Israel thought about using its nukes at one time.
So whatif France had nukes in 1940 and used them?
We suppose that, as after WWII, Germany has no nuclear weapons.
Let's say Manhattan project started in the thirties, the Joliot-Curie helped and, as a reward, the USA gave nukes to France (and GB).