Greenland was not part of the USA for a 150 years. It is also not mostly populated by ethnic Americans who speak English as their mother tongue. Nor is there a large American military base there that Greenland / Denmark is trying to evict them from and potentially hand over to a geopolitical adversary. Greenland is also an island a couple thousand miles away from Denmark.

Honestly, it is such a surprise that the difference is not obvious.