David Jackson

USA TODAY

TAORMINA, Italy – After ending an ambitious, nine-day international trip in the shadow of an active volcano on the Sicilian coast, President Trump returned to Washington this weekend to face the prospect of multiple political explosions.

As Trump inked arms sales with Saudi Arabia, tried to kickstart the Israeli and Palestinian peace process, met with the pope, and addressed European leaders, the ongoing FBI investigation into possible collusion between Trump's campaign and Russia continued to heat up at home.

As lawmakers seek more subpoenas from Trump's campaign and former associates for their own Russia investigations, the Trump administration must also deal with a potentially volatile Congress to push its plans for health care, tax reform, and major budget cuts. There's also a potential shakeup brewing in the White House itself, too, in part to deal with the barrage of explosive news reports, the Russia investigations and mounting congressional criticism.

Despite attempts to change the conversation at home with a splashy foreign trip, Trump is now back to reality.

The moment Trump stepped down from Marine One upon his return to the White House late Saturday night, the first question a reporter shouted was: "Mr. President, we hear you were trying to set up a back channel to the Russians."

While Trump and his White House deny any sort of collusion with Russians, and described the multiple investigations as "witch hunts," the president's first foreign trip was shadowed by major reports about the investigations. The FBI probe hit new heights this weekend after revelations that Jared Kushner, son-in-law and close adviser, had caught the attention of federal investigators for his contacts with Russian officials.

As Trump met with other world leaders at the G-7 summit, The Washington Post reported that Trump son-in-law Jared Kushner spoke with Russia's ambassador to the United States about setting up a back-channel between Trump's transition team and the Kremlin. The secure channel reportedly would have used Russian diplomatic facilities in an apparent move to shield pre-inauguration discussions from monitoring.

Trump at first appeared to try to stay on message, expressing nothing but confidence about his travels to the Middle East and Europe.

Addressing U.S. troops at a naval air station in Sicily, Italy, near the summit hosting the Group of Seven advanced economies, Trump said Saturday: "I laid out my vision for economic growth and fair trade in support of good-paying jobs, and even great-paying middle-class jobs, and more. And I called for much greater security and cooperation on matters of both terrorism, immigration, migration, to protect our citizens."

But he won't be able to keep that focus for long, experts say. "He looks forward to one thing – a major and growing investigation into collusion, obstruction of justice, and more," said Princeton historian Julian Zelizer. "The trip will be a blip compared to what's about to come."

The G-7 took place in the ancient mountain city of Taormina, very near the smoke-spewing Mount Etna – Europe's largest active volcano, and the inspiration for many a joke about the kind of trouble that looms over politicians.

In Trump's case, he's likely to respond explosion of tweets. After days of relative quiet on the Twitter front while traveling, Trump's account roared back into action after his return from overseas. The president seemed to anticipate future news stories by preemptively questioning their veracity; expect him to make his case on social media as stories about Russia and other items unfold in the weeks ahead.

"It is my opinion that many of the leaks coming out of the White House are fabricated lies made up by the #FakeNews media," Trump said in one tweet Sunday.

Yet the spate of reports on the Trump campaign's links to Russia have sparked lawmakers – including Republicans – to seek more information.

The Senate Intelligence Committee, conducting its own investigation of Russian involvement in last year's election, is now seeking documents from Trump's campaign reportedly all the way back to June 2015. And embattled former national security adviser Michael Flynn last week rejected a separate Senate subpoena for his communications with Russian officials, which have drawn the scrutiny of both the FBI and Congress. By asserting his Fifth Amendment right against self-incrimination, Flynn appeared to acknowledge he might still be in legal jeopardy with the FBI investigation, which could end in criminal charges.

The Capitol Hill drama only promises to get more intense. Lawmakers are also seeking public testimony from James Comey, the FBI director fired by Trump earlier this month as he was overseeing the Russia investigation. Comey may testify in the coming days or weeks.

Related:

Robert Mueller emerging as gatekeeper for all Russia probes, and Congress is wary

White House, DOJ miss Senate deadline to provide James Comey memos, records

Senate panel: Michael Flynn risks contempt of Congress

Comey is said to have notes of a February meeting with Trump in which he asked him to drop his inquiry into Flynn. Lawmakers are seeking the Comey memos, and administration requested more time beyond last week's Senate Judiciary Committee deadline to turn over the documents and any audio recordings of the president's interactions with Comey that might be maintained at the White House.

After Comey's firing, the Justice Department appointed ex-FBI Director Robert Mueller as special counsel to investigate the Russia mess – an assignment that could take months or even years.

To deal with all this, the president is also pondering a revamp to his communications team. The administration may assign a group of people to exclusively respond to questions about Russia stories, and may also cut back on the number of news briefings. The fate of Press Secretary Sean Spicer is also uncertain amid staff talk he's fallen out of favor with the president.

Investigations aren't the only potential firestorms hanging over the White House.

While Trump and Republican leaders celebrated the passage of a health care bill in the House, after months of uncertainty, they must still get legislation through the Senate.

Even some Republicans are balking at a plan that, according to a Congressional Budget Office analysis, would increase the number of uninsured Americans by 23 million by the year 2026.

Congressional Republicans are also objecting to some of the stark cuts in Trump's proposed budget, from State Department operations to Medicaid programs, which could hit especially hard the rural, working-class voters who overwhelmingly supported Trump.

Related:

Trump budget hard on 'forgotten' rural American supporters

CBO: House Obamacare repeal will increase uninsured by 23 million

Experts dispute Trump's argument that too many people are on food stamps

Most GOP members are sticking with Trump, but that could change if they perceive the president as a liability ahead of next year's elections to keep control Congress. The Trump factor gets a small test soon: A June 20 run-off to replace former U.S. Rep Tom Price, now Trump's health secretary. The Democrat is given a chance to win a Republican-leaning district.

That and other challenges are common to all presidents, however, and not just ones engulfed in multiple major controversies early in their terms.

It's the Russia drama, analysts say, that could haunt the rest of his presidency.

Citing the allegations against Kushner in particular, Republican analyst Rick Tyler had a short and simple explanation for what Trump is facing in the months and weeks ahead: "A political firestorm."