"Not only is the UN not solving the problems, it should - too often, it's actually creating new problems for us to solve," Trump said.
Trump took jabs at the U.N. General Assembly. Under his administration, the United States is stepping back from the back from the U.N. system it helped to create following World War II, says Craig Kafura, with the Chicago Council on Global Affairs.
"It's not that every president is a huge fan of the United Nations or multi-lateralism, internationalism. But this seems to take it to another level," Kafura said.
Trump has long sought to reduce immigration and abandon climate commitments inside U.S. borders but has spent less time advocating that other countries do the same thing. In the nearly hour-long speech, he globalized those priorities.
At times, the president was stern and combative, even attacking the U.N. and doubling down on his immigration policy, highlighting his administration's mass deportation efforts.
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"If you come illegally into the United States, you're going to jail, or you're going back to where you came from, or perhaps even further than that. You know what that means," Trump said.
Trump urged other leaders to follow suit, claiming what he calls "uncontrolled migration" a crisis, saying undocumented immigrants are ruining European countries.
"I can tell you I'm really good at this stuff. Your countries are going to hell," Trump said.
Stephen Maynard Caliendo, a professor of political science at North Central College, says despite the rhetoric, the U.S. still has a prominent place at the U.N. and the world stage.
"I think world leaders are used to the way Trump talks. I don't think anybody was surprised by it. It doesn't mean they accept it any better than they would, but I don't think there was shock in the room," Maynard Caliendo said.