Hamburg, Germany (CNN) In Warsaw, crowds waved American flags. In Germany, cartoonish effigies of the American President were hoisted instead.

For President Donald Trump, a second foreign trip was again a study in contrasts, the quick-shifting reaction to his controversial tenure encapsulating the divided world he and other leaders at the G20 summit confront.

Stopping for 15 hours in Warsaw, Trump found a confidence boost among the cheering crowds and like-minded government leaders. Delivering his first major outdoor address on foreign soil, he achieved a presidential moment, even as his message on America's view toward Europe diverged sharply with past US leaders.

In Hamburg, where the hum of police helicopters provided background music to violent protests, skeptical leaders and sleep-deprived diplomats, his touchdown was a hard landing. The yawning gap between the reception in each city was plain.

Officials said the originally peaceful protest became violent, with firecrackers and bottles being thrown at riot police.

Officials said the originally peaceful protest became violent, with firecrackers and bottles being thrown at riot police.

A banner on a bridge reads "President Macri, Don't sell our Argentina." Officials said at least 76 police officers were hurt.

A banner on a bridge reads "President Macri, Don't sell our Argentina." Officials said at least 76 police officers were hurt.

Participants in the protest. Police said one person had been arrested by late Thursday night.

Participants in the protest. Police said one person had been arrested by late Thursday night.

Police attempt to clear the street while using water cannons and pepper spray on demonstrators.

Police attempt to clear the street while using water cannons and pepper spray on demonstrators.

Protesters clash with riot police. The protest escalated throughout the day and evening.

Protesters clash with riot police. The protest escalated throughout the day and evening.

A man wearing protective goggles moves away from officers trying to clear the streets using water cannons.

A man wearing protective goggles moves away from officers trying to clear the streets using water cannons.

Police and protesters clash during the Welcome to Hell march.

Police and protesters clash during the Welcome to Hell march.

Police stand in front of the Rote Flora left-wing center as debris smolders in the street.

Police stand in front of the Rote Flora left-wing center as debris smolders in the street.

An officer looks on as barricades burn in front of the Rote Flora center.

An officer looks on as barricades burn in front of the Rote Flora center.

Protesters erect burning barricades in front of the Rote Flora, a left-wing cultural center, on July 6 in Hamburg.

Protesters erect burning barricades in front of the Rote Flora, a left-wing cultural center, on July 6 in Hamburg.

Riot police head down a road during the "Welcome to Hell" protest march on Thursday, July 6.

Riot police head down a road during the "Welcome to Hell" protest march on Thursday, July 6.

Protesters are visible through a hole in a destroyed window of a supermarket in Hamburg's Schanzenviertel district on July 7.

Protesters are visible through a hole in a destroyed window of a supermarket in Hamburg's Schanzenviertel district on July 7.

Protesters gather near a burning barrier during a demonstration against the G20 summit on Friday, July 7, in Hamburg, Germany. Protesters clashed with authorities as world leaders gathered for the two-day economic summit.

Protesters gather near a burning barrier during a demonstration against the G20 summit on Friday, July 7, in Hamburg, Germany. Protesters clashed with authorities as world leaders gathered for the two-day economic summit.

Not by accident, the first stop on Trump's two foreign trips have placed the President in a comfort zone, replete with adulation from leaders and new deals to announce between foreign governments and the United States.

Just as he did in Saudi Arabia this spring, Trump basked in the admiration mustered by Poland's right-wing government. Standing outside the security barricades, thousands of average Poles -- farmers, students, teachers and shopkeepers -- filled the streets and greeted Trump with cheers.

Many were bused into the capital from farflung provinces by civic committees, an attempt to deliver an enthusiastic welcome for Trump.

The tactic worked in the opposite way here in Germany. Filling the streets were protesters from across Europe, a contingent of tens of thousands who came here to disrupt the annual G20 summit by torching cars, smashing windows and clashing with fully equipped riot police.

Protests are a fact of life at almost all gatherings of major world leaders, and major summits like the G20 are often held outside of major cities where protesters can be kept far at bay. Here, the city center was gripped with sometimes-violent marchers, a level of unrest rarely seen in Germany.

Shuttling through Hamburg in his armored limousine, Trump caught no glimpses of the angry masses. But the demonstrators were successful in making themselves known; first lady Melania Trump was forced to cancel her participation in a program for leaders' spouses when the Hamburg police declared it unsafe for her to leave her building.

Mrs. Trump's spokeswoman said the turn of events was "unfortunate" since the first lady was looking forward to participating in the events. But the security situation did allow her to avoid a potentially awkward tour of a climate science center , which the husband of German Chancellor Angela Merkel had selected to show visiting spouses.

More comfortable in his role as global agitator

Trump has angered fellow leaders by withdrawing the US from the Paris climate accord, a position that further drove a wedge between himself and his counterparts at the G20. The inclusion of the climate center visit was in line with a larger effort here to isolate Trump on that issue and a host of other matters where he has broken with his predecessor, Barack Obama.

Merkel noted Trump participated in the first part of the session she organized about climate and "even made a contribution."

It was a signal that Trump has become comfortable in his role as a global agitator -- even as fellow leaders openly lament his moves on climate and trade, as Merkel and others did Saturday. While officials said he departed last month's G7 meetings in Sicily bruised by a climate lecture from his counterparts, he appeared less upset at the deep rifts between himself and other leaders this time around.

Trump's advisers intentionally kept Trump's European visit short; upon returning from his grueling first foreign swing, the President insisted future trips be curtailed in length. At the G20, however, Trump sought out leaders for one-on-one talks that amounted to a stacked itinerary.

"He made it more rigorous on himself," his top economic adviser, Gary Cohn, told reporters aboard Air Force One as Trump returned to Washington.

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At the G20, Trump appeared not to struggle with the myriad events where leaders are left to mingle amongst themselves. He clasped hands jovially with French President Emmanuel Macron instead of gripping him at length, as he did in May. He smiled and whispered with Merkel, whose hand he declined to shake in the Oval Office earlier this year. And, in a photo posted by the White House, he is seen laughing with Mexican President Enrique Peña Nieto, the president of the country Trump maligned most on the campaign trail.

There was no awkward elbowing, like during a NATO meeting in Brussels this spring. Even with Russian President Vladimir Putin, a veteran of calibrated body language, there were few outward signs of discord and, even more striking, there were actually signs of collegiality.

The first glimpse of the two men came from a clip posted on a German government Facebook page; the leaders appeared together toward the end of the rough video, which was set to an electronica soundtrack. Trump patted Putin's arm with his left hand as they shook. Putin pointed toward Trump with his left index finger extended.

It was the handshake the world had been awaiting. Later, during official talks that lasted more than 90 minutes longer than expected, aides anxiously glanced at their watches as the minutes ticked past. Melania Trump was escorted into the room in an unsuccessful attempt to bring the meeting to an end.

While Trump's body language signaled more comfort on the international stage, in other ways his lack of confidence in Germany was evident. Never was that clearer than in Trump's divergent posture with the press.

Trump never broke from his pointedly combative self on this second foreign trip, but a more comfortable-looking President took questions for the first time on international soil standing next to Polish President Andrzej Duda, a politician ideologically more simpatico with Trump.

"Do you have that also, by the way, Mr. President," Trump said turning to Duda, referring to an adversarial press corps.

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Out-spun by Russia?

After landing in Germany, though, Trump kept the press at arms length as world leaders debated -- and later agreed to -- a statement on key issues. As the G20 ended, one by one, world leaders, including Putin, Merkel and Turkish President Recep Tayyip Erdoğan, stepped behind podiums scattered around the Hamburg's Messe complex and took questions.

Trump was not one of them.

At one point, Putin -- whose high-stakes meeting defined Trump's first visit to Germany -- referred a question about Russian interference to the White House.

"I think it is better to ask him what you have asked, rather than me," he demurred.

When the reporter told Putin the White House had provided no answer, the Russian leader just laughed.

But the White House's silence was just as telling -- and consequential. Trump, unlike other world leaders, declined to use his bully pulpit abroad. His aides, too, were silent, declining to provide a single on-camera briefing during the three days in Germany.

And it hurt them. Minutes after Trump's meeting with Putin, Russian Foreign Minister Sergey Lavrov was on camera spinning the meeting, telling reporters that Trump accepted Putin's denial of meddling in the 2016 election.

Though White House aides would later deny that claim, their statements came without names and off-camera. After the Trump-Putin confab, it was the Russians who first controlled the narrative.

Despite the diplomatic row that ensued following Trump's meeting with Putin, top White House aides said afterward that they viewed the trip as a success.

"President Trump has had a very, very significant few days," Treasury Secretary Steve Mnuchin told reporters. "I would just generally say we've had a very productive economic meetings. There have been very substantive issues discussed."

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Back to health care

The trip may have seemed like a respite for Trump, but he arrived back to a complicated capital city where questions about Russia's 2016 meddling have only grown since the Putin meeting.

Even more pressing: The future of the Republican health care bill.

As the President was away, the fate of the Trump-backed plan to repeal Obamacare grew more desperate, with Republican senators telling constituents at town halls that they remain against the plan.

Senate Majority Leader Mitch McConnell, in a comment that caught Trump aides off guard, told constituents in Kentucky that if Republicans are unable to pass a replacement they will be forced to work with Democrats to prop up the current health care system.

"If my side is unable to agree on an adequate replacement, then some kind of action with regard to the private health insurance market must occur," he said.

Trump, a President not known for his interest in the policy intricacies of a sweeping bill like health care reform, will now be presented with a detailed Rubik's Cube of conflicting Republican desires for the health care bill.

Time is short. After three working days in Washington, the President heads back to Europe on Thursday for a quick trip to France for Bastille Day celebrations with French President Macron.