From using negotiations as a ploy for surprise attacks to murdering heads of state and casually reneging on American commitments — including his own — Trump’s damage to US diplomacy will be evident for years. Trump’s collaboration with Israel to launch an unprovoked war on Iran is manifestly among the worst foreign policy decisions in the history of the American republic. “Trump’s move demonstrates that the United States cannot be trusted to keep its promises,” the Belfer Center’s Martin Malin said at the time. That’s the case with the June 17, 2026 Memorandum of Understanding between the United States and Iran, which Trump signed at the Palace of Versailles. Critically, Trump’s behavior bolsters the credibility of hardliners in the Iranian government who’ve repeatedly argued that the United States cannot be trusted and shouldn’t be negotiated with.