Can he pull out of NATO without approval from congress?
It would seem odd if just one man could do that?
In effect he already has. When he declared how NATO won't help bail him out of a mess or his own creation that goes on to suggest he won't be there for NATO. Yesterday Hegseth "Defense Secretary Pete Hegseth declined on Tuesday to reaffirm the U.S. commitment to NATO's collective defense". Just questioning whether they'd honour Article 5 is enough to make NATO in its current form "dead".
Time for Europe to get on with setting up their own defence alliance, NATO minus US. It becomes irrelevant who is President after Trump, that it has happened means it can happen again. US is no longer a reliable ally and we need to get on with sorting ourselves out without US.