President Donald Trump listens to Japan's Prime Minister Shinzo Abe speak during their meeting, Nov. 30, 2018 in Buenos Aires, Argentina.
President Donald Trump listens to Japan's Prime Minister Shinzo Abe speak during their meeting, Nov. 30, 2018 in Buenos Aires, Argentina.

Just minutes after he landed in Argentina for the G-20 summit, U.S. President Donald Trump made clear there were other things on his mind besides the meeting of the world's leading economies.

Shortly after disembarking from Air Force One, Trump sent a pair of tweets slamming the investigation of special counsel Robert Mueller, demanding he instead look into the "real crimes of the other side." 

Just a few hours later, as the sun was still rising on the first morning of the G-20 gathering, Trump sent two more tweets on the same topic, suggesting a preoccupation with domestic — not international — affairs.

Of course, Trump is not the first U.S. president to address domestic events while overseas. U.S. presidents travel with an entourage of White House reporters that frequently ask U.S.-focused questions. 

But on his international trips, Trump places an unusually heavy emphasis on domestic affairs. When combined with an "America First" foreign policy that downplays the importance of multilateral institutions, Trump's approach can complicate forums like the G-20.

"I just don't think President Trump is interested in the agenda of international cooperation at this summit," said Mark Simakovsky with the Atlantic Council. "He's more interested in having it as a venue where he can promote his own national and foreign policy." 

Trump's tweets suggest he is especially concerned about Mueller's investigation that is looking into possible links between Trump's 2016 presidential campaign and Russia, which tried to interfere in the election.

On Thursday, Trump's former lawyer, Michael Cohen, pleaded guilty to misleading lawmakers about the timing of talks for a tower that the Trump organization was trying to build in Moscow. 

Russian President Vladimir Putin, left, listens as
Russian President Vladimir Putin, left, listens as France's President Emmanuel Macron speaks to him at the G-20 summit in Buenos Aires, Nov. 30, 2018.

Rising nationalism

Trump isn't the only thing impeding multilateral cooperation. From Brazil to Russia, rising global nationalism has complicated international efforts on a wide range of issues, including trade and climate change. 

But Trump has a unique ability to attract attention often hurling insults at world leaders before, during, and after his foreign stops. That alone hurts forums like the G-20, many analysts say.

In June at a G-7 summit in Canada, Trump engaged in confrontations with his counterparts over his steel and aluminum tariffs, before leaving early and failing to sign a joint communique. On his way out, Trump blasted Canadian Prime Minister Justin Trudeau as "meek and mild." 

Earlier this month, Trump skipped a World War I ceremony in Paris, citing traffic and bad weather. While in France, Trump instead tweeted about recent U.S. midterm election results, among other topics. After leaving, Trump noted French President Emmanuel Macron's "very low approval rating." 

President Donald Trump, center, sits between Canad
President Donald Trump, center, sits between Canada's Prime Minister Justin Trudeau, right, and Mexico's President Enrique Pena Nieto after they signed a new U.S.-Mexico-Canada Agreement that is replacing the NAFTA trade deal, Nov. 30, 2018.

USMCA success

Trump has scored some multilateral achievements. 

On Friday, Trump joined Canadian Prime Minister Justin Trudeau and Mexican President Enrique Pena Nieto in signing the recently agreed upon trade deal between the three countries. 

The deal, which only followed often publicly contentious negotiations, now must be ratified by lawmakers in all three countries. 

"This has been a battle, and battles sometimes make great friendships," Trump told his counterparts during the ceremony. But he called the deal a "truly groundbreaking achievement." 

President Donald Trump arrives to speak at a campa
President Donald Trump arrives to speak at a campaign rally at the IX Center, in Cleveland, Nov. 5, 2018.

Everyone else first, too?

Trump's "America First" approach also is causing other nations to become nationalistic in international settings, however, like the G-20, according to Roberto Bouzas, a professor at Argentina's Universidad de San Andres.

"If the U.S., which is the most influential international actor, publicly states that what matters most and only is its own national interest, then it doesn't make much sense that the rest of the world says something different or acts in a different way," said Bouzas.

White House officials say that's OK, insisting that every country is free to look out for its own interests. 

But that approach doesn't work as well for some smaller countries, others insist.

"If multilateral institutions, multilateral rules fade away, that's not good for us, because we are small and we need rules in order to perform better," Bouzas said. "If we are left to power politics only, then we are on the losing side."