France sends 15 soldiers, Germany sends 13 soldiers - tiny numbers, sure, but 15 and 13 more, respectively, to defend against a possible threat than either of those countries sent in the years since Russia rolled into Ukraine.
In any case, the point stands: I would argue that France is willing to put a dozen soldiers in Greenland because it is pretty sure that they won’t be killed by the US, as opposed to sending even a single soldier to Kiev where there is a reasonable chance that they might get killed and we might have to do more than just send money and guns.
If the U.S. seized Nuuk, and Europe mustered a counter-invasion, it would be comparable.
How is that obvious? Unless you have invested in a post-WW3 world.