If the new U.S. administration was interested, it could do a number of things to promote world peace.  These include improving U.S. relations with Russia and China, moving forward with nuclear arms control and disarmament, and drawing upon the United Nations to handle international conflicts.  Although, given the militarist inclinations of the new administration, little of this seems likely to become U.S. public policy, progress along these lines could be made if enough people demanded it.