Let's be clear, if Trump was opposed to NATO, he'd leave it like he did the Paris Climate Accord and the Trans Pacific Partnership. Far from being opposed to NATO, he'd like it to actually be militarily significant, which it currently is not.
Today NATO is largely a multinational "fig leaf" existing to make U.S. military actions seem to represent a multinational consensus. Trump wants other far-from-poor nations to pull their own weight in the alliance, to contribute meaningful military muscle, to maintain real air power and armor, for example.
I suppose, if they flatly refuse to develop effective militaries, he could eventually become disillusioned and leave NATO. Right now he is busily trying to get them to live up to their treaty commitments, to spend a minimum of 2% of GDP on their military. I expect him to succeed, or failing that, eventually ask the nations which refuse to comply to forfeit their NATO memberships.
If the other nations of Europe want to create a "carve out" for Germany - given 20th century history many would prefer it never again have a meaningful military - then they need to make up the substantial difference with their own spending.
