President Donald Trump participates in a United Nations Security Council briefing on counterproliferation at the United Nations General Assembly, Wednesday, Sept. 26, 2018, at U.N. Headquarters. (AP Photo/Evan Vucci)

President Donald Trump figuratively gave the United Nations the back of his hand this week in a brief appearance before the General Assembly. He showed up late, rejected globalism in a speech to world leaders, and briefly chaired a Security Council meeting on the proliferation of weapons of mass destruction.

His approach did not endear him to either audience, and he seemed to say he could not care less.

His presentations were largely a laundry list of his accomplishments, including the boast that his administration had accomplished more than “almost any in the history of our country,” a bizarre assertion that drew laughs, which he shrugged off. He also strongly defended national sovereignty and criticized U.N. institutions that he said violated sovereign principles, like the International Criminal Court.

And at the Security Council he criticized China, a nation he had praised in his General Assembly speech, saying it was interfering in U.S. politics — an apparent reference to Chinese tariffs targeting farmers in precincts that voted for Mr. Trump in 2016.

In effect, he said, his administration does not play the United Nations’ game.

The United Nations wants the United States to play by its rules, but it does not like to take on difficult issues. President Barack Obama won the Nobel Peace Prize — an expression of the general view held at the U.N. — simply by not being President George W. Bush, whose largely unilateral invasion of Iraq in 2003 set off what has now been 15 years of regional turmoil.

As a result of the Bush war initiatives, combined with the rising cost of entitlements, particularly health care, Mr. Obama at the beginning of his administration faced what he considered an overextended military and tight budgets. His solution was what one of his aides called “leading from behind,” attempting to draw Europe into a more active role in dealing with the Middle East, while cutting U.S. commitments there.

His approach did not work. The allies were not prepared to become deeply engaged for the long haul, and the reduction of U.S. forces in Iraq just added to the instability. Mr. Obama’s drawing Iran into an agreement to reduce its inventory of enriched uranium and temporarily submit its nuclear industry to international supervision was applauded by Europe because it viewed Iran as a promising market.

But Europe proved itself reluctant to take steps against Iran’s use of assets liberated by the agreement to increase its aggressive involvement in the Middle East and to accelerate development of ballistic missiles.

When he took over from Mr. Obama, Mr. Trump inherited the Middle East turmoil, an aggressive Iran and a run-amok North Korea. He also inherited a world trading system characterized by blatant cheating, particularly by China. He tried to get Europe to agree to do something about Iran and failed. He also encountered European resistance to lowering trade barriers against U.S. goods.

So Mr. Trump struck out in his characteristically combative way, rejecting the Obama Iran deal, threatening North Korea, slapping tariffs on countries right and left, and abandoning decades of diplomatic formulas for dealing with the peace process between Israel and the Palestinian state. When he defended national sovereignty to the General Assembly, he was speaking about his right to be assertive. It was not something the assembled heads of state wanted to hear.

Since we do not yet know the outcome of the many fights he has picked, and based on the notable early accomplishments of some prior presidencies, it was ridiculous for Mr. Trump to claim historic successes.

But the international system of law and the United Nations too often have failed to cope with bad actors and chaos in the international environment. Mr. Trump is trying to change things for the better, and despite his problematic approach and sometimes clumsy diplomacy, he at least deserves some respect for his efforts.