President Trump cancels Obama's deal with Australia to accept 1616 detainees now held in offshore camps

Before former President Obama left office he made a deal with the government of Australian PM Malcolm Turnbill to accept some 1616 detainees now held on the offshore islands of Manus and Nauru.  Held there, because they pose a possible danger if admitted into the Australian general population.  However, our ex-president in his infinite wisdom would have allowed these detainees deemed unsuitable by Australian authorities into our nation.  Needless to say, President Donald Trump put an end to this Obama madness by refusing to take in these detainees who numbers almost certainly contain some with anti-American views or have wrapped themselves in the banner of Islamic extremism.  Trump in a recent phone call to the Australian PM informed him the deal was cancelled.  This, of course, brought about criticism from those in the media who accused Trump of being undiplomatic to the Australian leader.  The truth about that recent phone call between the two leaders is that both men are looking out for the welfare of their own people.  Neither leader wants these detainees set loose in their nation.  So I ask, what did Trump do wrong?