He supports it... but if they're doing a "bad job" he will be very "sad!" when he has to withdraw from it.
Pretty sure NATO is an actual treaty, which means the Senate would have to vote on withdrawal, and at the very least McCain, Graham, Flake, Murkowaki, Rubio, and Corker would vote against.
Why would the Pussygrabber regime pay any more attention to treaties, than to the Constitution and court orders?
...because every adversary (and frienemy, and even the pluckier allies) of the US will also decide to ignore the treaties which enshrine the US as the world's dominant power?