So these soldiers are there to undermine the US narrative that Greenland is 'undefended', thus eroding the rationale for a US takeover. However, we have seen that the US national security can be made to fit any future imagined scenario, so we can expect US troops also to fly in. Then what? Can't see how Europe is going to do anything here, bluffing with no hand to play, which has become standard pro forma

These troops have been invited, which makes a legal difference (at least for all those who still believe in the rule of law); see https://news.ycombinator.com/item?id=46630190

As far as I am aware, although Operation Arctic Endurance is pitched as being in the interests of NATO, it is technically not being run via NATO.

yes, under NATO command means under US command, so this is significant. Still, it reminds me of the Dutch deployment of UN peacekeepers in Sarajevo - if and when it comes down to it, they will leave without firing a shot

Whether defenders fire shots is immaterial; what matters is if or when they become targets of an armed attack.

Recall that art 3(c) means invaders would also not have to fire any shots to commit an act of aggression: establishing a blockade suffices.

The Netherlands bought the military hardware they needed to run their own CAS after that episode.