Historically, it isn't Canada that's been threatening to leave NATO.

Erm, they can stay in NATO with the other European members just fine. It's the US that is making noises about leaving. NORAD is another matter, but the US and Canada can each run their own radars - the targets are south of the 49th parallel for the most part.

NORAD relies on radar stations in Canada.

No, it’s a lost sale.

This comment is like a poem encapsulating American hubris.

The American head of state threatened to invade and annex the country, and you boil that down to a sarcastic "America bad"?

America threatened both Canada and Greenland. Both NATO countries. It is engaged in murders of boatsmen, it started an illegal war that literally harmed countries around the world, it kidnapped a president just so it can blackmail is former right hand and is intentionally causing humanitarian catastrophe in Cuba to blackmail its government.