In opening the prospects, however distant, for a reunification of the Korean Peninsula, the Singapore meeting did — at least in appearance — sideline Russia and even China. But was the United States still acting as “the West” in doing so? Or had it also sidelined its own allies, which include South Korea and Japan?

Keep in mind yet another summit meeting — in Canada with the Group of 7 powers, all Western-allied — that immediately preceded the Singapore meeting. Mr. Trump essentially dismantled the collective “West” by throwing that gathering into disarray over tariffs and the Iran nuclear deal. He then flew to Singapore and elevated Mr. Kim to a respectable world statesman.

For decades, the united West saw the Kim dynasty’s totalitarian principality as a murderous anti-Western dictatorship. But if you take away the unity, the values of the West disappear with it. So does any “anti-West.” And persecution on political and religious grounds, abductions of other countries’ citizens, extreme brutality by the North Korean regime and similar issues were conspicuously absent from Mr. Trump’s remarks at a news conference after the talks in Singapore. He said he had raised those subjects with Mr. Kim, but then made it clear that denuclearization had taken precedence over human rights.

For his part, Mr. Putin, speaking to Chinese reporters in Qingdao, called Mr. Trump’s decision to meet Mr. Kim “very brave and mature.” Mr. Putin’s detractors in Russia reacted differently. “The meeting was depressing to watch,” Leonid Volkov, who is active in opposition politics, wrote on Telegram, Russia’s social networking app. “It’s hard to forget that this amenable fatty is the commandant of the world’s largest prison camp,” he said, referring to Mr. Kim.

China was not entirely absent from the lead-up to the Singapore talks. To be sure, Mr. Kim was the first to signal, in March, a willingness to discuss with America the fate of Pyongyang’s nuclear program — an invitation Mr. Trump greeted enthusiastically. But later that month, Mr. Kim traveled to consult President Xi Jinping, and they met again before the summit.

It also is significant that the Singapore agreement’s terms were left vague, and that any detailed discussion that may now follow would have to include China, which accounts for 90 percent of North Korea’s trade volume and most of its energy supplies.

In addition, Beijing and Moscow are wary of the possibility of a future American effort to topple the North Korean regime. Pyongyang’s complete denuclearization in exchange for a guarantee of regime security is derided by some in Moscow as a “Libyan model,” the Russian foreign policy commentator Vladimir Frolov wrote recently. Mr. Kim is of course aware of this view, and Mr. Trump assured him of security.