 We had a good, we had a productive meeting, and of course there is no way to make these big decisions on how to further strengthen NATO, enlarge NATO, new members, without having a strong U.S. leadership. One of Trump's former national security advisors, John Bolton, says Trump in a second term would work to get the U.S. out of NATO. Congress passed legislation last year making that harder, but a president could simply stop collaborating in some or all of NATO's missions.