Singapore (CNN) President Donald Trump returned to Washington on Wednesday to piece together a new world reality, one he hopes will result in a nuclear-free North Korea and maybe one day a Nobel Peace Prize. But as his estrangement from traditional US allies deepens and the outcomes of his summit with Kim Jong Un are disputed, an uncertain and challenging road is coming into clearer view.

After spurning close US partners at the G7 summit in Canada over his sense that the US is being cheated on trade, Trump turned to touting his historic summit with Kim as an unmitigated success that will quickly lead to North Korea abandoning its nuclear weapons -- even though the regime offered no new concessions or verifiable commitments on paper.

Now, Trump's work begins to ensure the new American outlook he's projected onto the world endures. It's one where bipartisan members of Congress are doubting the outcomes of his Singapore summit , while repudiating his rapprochement with Russia and his alienation of US allies . Meanwhile, the world awaits the concrete outcomes of the detailed US-North Korea negotiations that will decide whether Trump's optimism was simply borne out of naiveté.

The President travels to Europe in a month to reckon with a fractured set of alliances, his decision to spurn loyal Western allies deepening the fissures in that longstanding partnership.

At least some level of participation by that group -- which collectively applied enough pressure on Pyongyang to come to the negotiating table -- will be necessary if Trump's nuclear gamble is to succeed.

So, too, will cooperation from Russia and China, the two countries with the largest trading relationships with North Korea who also happen to be among the most fraught US foreign relationships -- never more so with Trump. Already, Moscow and Beijing have released some of the pressure. A senior administration official said ahead of Trump's summit that it's likely the global sanctions on the rogue regime erodes further.

Secretary of State Mike Pompeo is bound for Seoul and Beijing this week to explain what, precisely, Trump's summit with Kim achieved. Trump will likely do the same when he next travels abroad in July, to a NATO summit in Brussels and his long-delayed visit to the United Kingdom.

"There's never been anything like what's taken place now," the President proclaimed Tuesday as Pompeo and other top aides looked on adoringly. "I think he might want to do this as much or even more than me because they see a very bright future for North Korea."

As he touched down at Joint Base Andrews outside of Washington early Wednesday, Trump sought to amplify his achievements in a series of tweets.

"Just landed - a long trip, but everybody can now feel much safer than the day I took office," he wrote. "There is no longer a Nuclear Threat from North Korea. Meeting with Kim Jong Un was an interesting and very positive experience. North Korea has great potential for the future!"

"Before taking office people were assuming that we were going to War with North Korea," he went on. "President Obama said that North Korea was our biggest and most dangerous problem. No longer - sleep well tonight!"

The President's reality

JUST WATCHED Trump talks denuclearization, sanctions and Kim Jong Un Replay More Videos ... MUST WATCH Trump talks denuclearization, sanctions and Kim Jong Un 02:07

But that was only the President's reality, one that he had forged on a hefty dose of optimism, wishful thinking and the private assurances of North Korea's 34-year-old dictator.

It will only become a reality for the world if Kim bucks precedent and follows through on his broad pledges and the lead of a one-time nemesis twice his age. But for now, the truth is that Kim signed off only on an "unwavering commitment to complete denuclearization" -- one North Korea has previously made as recently as a month and a half ago -- and secured no written commitments to specific, verifiable actions on denuclearization or human rights.

Yet one thing is new in the burgeoning Trump-Kim relationship: face-to-face flattery. It was difficult to tell Tuesday which leader was more susceptible to being charmed, but it certainly could have been Trump, who emitted effusive praise.

The President's towering proclamations were bolstered by the made-for-TV optics of the first, indisputably historic meeting between a sitting US president and North Korean leader: Two men, who months ago appeared to be on the brink of nuclear war, shook hands, patted each other on the back, smiled, laughed and even strolled together through a garden like two old friends burying the hatchet, producing a palpable sense of good will. Each man signaled the prospect of inviting the other back home.

Despite the lack of printed North Korean concessions, Trump offered one of his own, vowing to end the "provocative" -- to steal a term used by the North Koreans -- joint military exercises regularly conducted between the US and South Korea.

The perils of Trump's follow-his-gut approach to North Korean diplomacy quickly became apparent. Even as Air Force One headed back for the long journey to Washington, confusion spread as Republicans tried to explain -- and understand -- just what the President had done in Singapore.

It was clear the President hadn't fully briefed US military brass or his allies about his plan to cancel joint military exercises in South Korea. And it was noted that he derisively described the drills as "war games," remarkably adopting the language of Pyongyang over the Pentagon.

Vice President Mike Pence raced to Capitol Hill to try and bring Republicans up to speed, but the message became lost in translation.

Within hours of Trump claiming North Korea had given up "a tremendous amount," Sen. Lindsey Graham, R-South Carolina, offered a dramatically different answer when asked what North Korea had given up.

"Nothing yet," Graham said bluntly. "This is a first step, this is a good start, but we're a long ways away from an agreement."

Seduced by history

JUST WATCHED Trump meets Kim Jong Un for unprecedented talks Replay More Videos ... MUST WATCH Trump meets Kim Jong Un for unprecedented talks 02:17

From the moment he accepted the invitation to meet with Kim, walking into the White House briefing room on March 8 with a wide smile, Trump seemed caught up by the potential for making history.

That sentiment played out in real time -- for all the world to see -- as Trump shook hands with Kim, smiled and reveled in the moment Tuesday.

"It's my honor," Trump said. "We will have a terrific relationship. I have no doubt."

But the doubts were plentiful in the wake of the Singapore summit.

While even many of Trump's biggest critics offered rare praise -- that talking and the prospect of diplomacy are far preferable to a nuclear standoff -- the pivotal question going forward remained: Is the President so thirsty for a deal that he gives away far more than he gets in return?

In the months before the high-stakes meeting, Trump took detailed interest in the planning for the event, including how it would look on television when he shook hands with the longtime US adversary. White House advance teams planned the moment precisely to meet Trump's specifications that the episode appear monumental. Images were mocked up to show the President what the handshake might look like on camera.

But the optics were largely a significant win for the North Koreans, who have long sought the legitimacy of a meeting with a sitting US president, presenting the US and North Korea on level footing -- something the officials from Pyongyang who negotiated the summit logistics with US counterparts were "very conscious" about, according to a US official involved in the discussions.

The US largely agreed to North Korea's demand for parity in all aspects of the summit, from the number of officials during the bilateral meetings to the number of US and North Korean flags side by side during the arrival ceremony -- a boon for North Korean propaganda.

Trump stepped out onto the stage for his hour-long celebratory news conference on Tuesday after the dramatic airing of a movie trailer-like video that presented a glowing portrait of himself and Kim and clips of happy North Koreans, adoringly cheering their leader. With a Secret Service agent dutifully standing guard, the video first aired in Korean, leaving American reporters to raise their phones to capture the footage, wondering if they were watching North Korean propaganda.

The video, Trump later revealed, was perhaps his most prized piece of summit production, a video that he showed Kim on an iPad screen during their meetings to present him with the stark choice between military confrontation and Singapore-like modernity and prosperity in North Korea.

"I think he loved it," Trump said, even though "we didn't have a big screen like you have the luxury of having."

Even as the summit was occurring, Trump did not give up his role as the event's executive producer. As photographers snapped him sitting down for lunch, he checked to ensure they were taking flattering shots.

"Getting a good picture, everybody?" he asked. "So, we look nice and handsome and thin? Perfect."

A sharp contrast

JUST WATCHED Trump plans to depart G7 summit early Replay More Videos ... MUST WATCH Trump plans to depart G7 summit early 02:26

The conviviality stood in sharp contrast to the President's earlier summit in Canada, where imagery of frustrated western allies crowding around a smirking Trump was quickly distributed by the German chancellery. After Trump met with his French counterpart Emmanuel Macron, photographs of the white marks Macron's thumb left on Trump's hand went viral.

At the red-shingled Capella hotel, the grip wasn't quite as tight. But Trump's repeated praise of the North Korean leader, his trumpeting of a still unwritten denuclearization agreement and the sense of history he imparted as he told even the press in the room "congratulations to everybody" could come back to bite Trump, similarly to how President George W. Bush came to regret his "mission accomplished" moment.

In many ways, the Singapore summit was the easy part. The true challenge, of course, will be to keep the momentum alive and to press North Korea into concrete steps to verify any dismantling of the nuclear program.

The two leaders' handshake made history, to be sure, but it remains an open question whether their agreement will.