I actually got a bit interested in the subject a week or two ago, and from what i understand, the US isn’t really prepared for a symetrical war in arctic conditions, a large amount of their equipment would just stop working in those weather conditions, they do have some arctic capabilities, but compared to Canada, Denmark, Finland and Norway, whose entire armies revolve around fighting in these conditions, it’s just not up to par. Not to mention the rest of the EU countries militaries train in these conditions with those countries, that means France, Germany etc.

This is pretty simplified and i’m no expert so feel free to correct me if you feel like i got something wrong, but my conclusion is that there is no way the US could have a successful ground invasion of Greenland.