As others have pointed it out it's about splitting NATO.
My real concern is Canada. Trump has made similar remarks about Canada like he did Greenland. If he takes Greenland it will be much harder for the EU should resupply Canada should the US see Canada is fully surrounded. How do Canadians view this?
What does it mean to "surround Canada" and why would anyone want to do it?
Almost the entire population of Canada is huddled against the US land border. Greenland is very far away from where the action would be if the US "takes" Canada. There would likely be few shots fired; Canada lacks the ability to put up a credible defense. The EU has no capacity to resupply Canada in any case. The whole scenario makes bizarre assumptions.
I don't think most Canadians consider the US "taking" Canada to be a serious scenario outside of echo chambers among the "too online" crowd. What would that gain the US that it doesn't already have?
What does the US gain from taking Greenland that it doesn't already have? If the US does invade an ally to acquire territory I think Canadians should be worried. In any case, what the US gains is the wrong perspective. This is about Trump and those around him wanting to build an empire and the American people, seemingly, letting them.
Although the probability is closer to 0% than 100%, it is far enough away from 0% to have many Canadians concerned. As the midterm elections approach and things start looking like he's drowning, Trump will grasp for any convenient distraction, the bigger the better. Canada is uncomfortably on the short list.
My real concern is Canada. Trump has made similar remarks about Canada like he did Greenland. If he takes Greenland it will be much harder for the EU should resupply Canada should the US see Canada is fully surrounded. How do Canadians view this?