When Donald Trump stood beside the Irish Taoiseach in Dublin and mused aloud that a united Ireland 'may as well happen now,' he did not announce a policy — he disturbed a silence. For decades, American presidents had treated Ireland's constitutional question as a matter for its own peoples to resolve, a restraint born of hard-won peace. With characteristic casualness, Trump set that tradition aside, reminding the world how fragile diplomatic equilibrium can be when power speaks without discipline.