US President Trump has threatened to leave the North American Free Trade Agreement. How much would each member country gain or lose if this threat were carried out? Would trade imbalances within the region diminish? What would the transition to new production and consumption patterns look like? I provide quantitative answers to these questions using a dynamic general equilibrium model with a multi‐sector input–output production structure, heterogeneous firms that make forward‐looking export participation decisions, and adjustment frictions in trade and factor markets. Regional trade flows would fall dramatically, and while the US trade deficit with Canada would decline, the deficit with Mexico would grow. Welfare would fall by 0.04%, 0.12%, and 0.2% in the United States, Canada, and Mexico, respectively, and transition dynamics would significantly affect welfare in both the short run and the long run.