Additionally, it's helpful to know the specific language used in Article 5:

Article 5

“The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence recognized by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area.

Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.” (emphasis added)

Article 5 doesn't actually oblige NATO members to defend anything by force, it obliges NATO members to decide what actions are "deemed necessary" and then to undertake those actions. If a NATO member gets invaded, everyone could -- in theory -- write a sternly worded letter and call it a day (though I doubt that would be the actual response). As you/others have more or less said, the actual action chosen would largely be the result of political will.

Even during the recent occupation of Ukraine and the threat upon neighboring countries that are in NATO there was discussion about what-ifs, and how much gray area there is in such events. The core idea of NATO was about deterrence, much like the MAD of nuclear weapon buildup. If someone crosses that line, something has to happen otherwise the whole agreement is called out as meaningless. Article 5 leaves what actions need to happen open ended though, so assistance can be something as simple as persuading the attacker to leave via strong words. Which will absolutely be the first thing tried, as no one wants to escalate to the next level. Well, except the idiots who are attacking.

To your point, I think the political will to defend Greenland will definitely be there from the overwhelming majority of other NATO states.

Yeah. The invocation of Article 5 for Afghanistan showed a mixed response from the various NATO nations in what support they would provide.

And since it's basically the US and everyone else in equal share, NATO is just dead and irrelevant if they're the ones breaking it.

The EU, on the other hand, would probably be in like a dirty shirt, having a defence agreement aspect. Maybe Canada too, just because we'd know we're next.

In practice, it would be the end of NATO.

Greenland is part of NATO just the same way that all other Danish territories are.

Greenland is not a nato member

That's like saying your right arm isn't a human.

Greenland is simply a part of Denmark, so it is a NATO member.

But Denmark is deemed legally to protect its autonomy which is a nato country. It's a strange case...

I know it’s not the best source from what I read on the Wikipedia article Greenland being a Autonomous territory of Denmark is apart of Denmark and therefore a NATO member

Yeah, it's a no win. Either NATO becomes ineffective because it won't honour it's agreement or WW3 starts.

I've never seen my former prime-minister been referenced as that :') - most certainly not my political colour, but why CIA pig vermin? He is most certainly a competent manager of the status quo, but as a leader spineless and without a vision (for a better world)

Kind of like Czechoslovakia in WW2.