The lesson is clear. You cannot delegate your defense to others if they are in competition with you. I don't understand why my comment got so many downvotes. I would have appreciated a discussion on the topic instead.

The real estate sales guy is also trying to sell the idea that Europe has no own defense, which is simply untrue.

Europe (excluding Russia) has the second most powerful military in the world on most accounts, with proper technological replacements for everything sold by the Nato ally on the other side of the Atlantic. (Much thanks to Charles De Gaulle who knew the Americans could not be trusted).

But a war with the Moscow State going on in Europe is a big thing. Which of course makes Europe weak in the west, and can be taken advantage of.

I think the lesson learned here is that Europe (and Canada) needs to close ranks and unite. Which may not be a preferable outcome for USA. And before T with a functioning Nato command, there were simply no reason to do that.

Re Greenland, we were in cooperation with the US for decades and the US has had its largest overseas base in Greenland in a friendly way for the free world to protect against the Russian and similar dictators. I'm not quite sure of the lesson there. Do not cooperate with friends of many decades because they may turn on you one day?