Donald Trump once again showed friend and foe alike on Thursday that the United States is no longer a reliable negotiating partner.Trump's decision to abruptly cancel next month's summit with North Korean leader Kim Jong Un may very well have been the right call at this point. But the way the president went about it will likely have second and third order consequences that he does not appear to have grappled with, from empowering China to straining alliances and undermining future nonproliferation efforts.