Obviously I don't agree with his threats over Greenland, but acting like the end of NATO would be a huge loss for the US is ridiculous. Look at how obsequious European heads of government are towards Trump, even in the face of these threats; that tells you all you need to know about whom NATO truly benefits. They know if the US withdraws from Europe completely, they'll have to up their military spending considerably to plug the gaps, which will strain the welfare state.