While Democrats have said Barr's letter should not be considered the final word on what Mueller found, Trump still claimed total vindication.
He said today that "we can never let this happen to another president again".
As he has many times before, he suggested the investigation was tainted from the beginning and said it was a "terrible thing".
He even accused those responsible for launching it of "treasonous things against our country" and said they "certainly will be looked into".
Trump has spent months railing against former Justice Department officials, including former FBI Director James Comey, accusing them of an illegal witch hunt for the purpose of delegitimising his presidency.
He has also falsely claimed that the investigation was based on memos compiled by former British spy Christopher Steele, and even blamed former Senator John McCain, who died last year, for passing the memos to the FBI.
But the investigation began months before the FBI ever saw the dossier — and the FBI already had a copy by the time McCain turned it in.
Trump, asked today if he'd be okay with the release of the full report, responded: "Up to the Attorney-General, but it wouldn't bother me at all."
Republicans followed Trump's lead, with Senate Judiciary Committee Chairman Lindsey Graham promising to "unpack the other side of the story" of the Russia investigation.
Graham, who spent the weekend with Trump in Florida, said his committee will investigate the actions of the Justice Department in the Russia investigation, including the FBI's use of the Steele dossier.
Graham's comments echoed Trump's own complaints in which he compared the probe to a failed coup and said those behind it should be held responsible. But Graham wouldn't go quite as far, saying he believed that the Mueller investigation was legitimate and had to happen in order to answer questions about Russian interference in the 2016 election.
The South Carolina Republican also had a warning for Trump using his pardon power to help those who were ensnared by Mueller's investigation.
"If President Trump pardoned anybody in his orbit, it would not play well," Graham said.
Among those whom Mueller charged during the course of his investigation were the President's former campaign chairman, Paul Manafort, and his first national security adviser, Michael Flynn.
Five Trump aides pleaded guilty and a sixth, longtime confidant Roger Stone, is awaiting trial on charges that he lied to Congress and engaged in witness tampering.
White House aides and allies blanketed television news broadcasts to trumpet Barr's letter and claim that Trump had been the victim in a probe that never should have started.
Democrats said they were still waiting for the full report, in addition to the underlying evidence that Mueller used.
"The fact that Special Counsel Mueller's report does not exonerate the President on a charge as serious as obstruction of justice demonstrates how urgent it is that the full report and underlying documentation be made public without any further delay," House Speaker Nancy Pelosi and Senate Democratic Leader Chuck Schumer said in a joint statement.
"Given Mr Barr's public record of bias against the Special Counsel's inquiry, he is not a neutral observer and is not in a position to make objective determinations about the report."
Given the report, Democrats seemed more likely to focus on their ongoing investigations, calls for transparency and frustrations with Barr, rather than engaging with the talk of impeachment that has been amplified on Pelosi's left flank.
As the release of Mueller's report loomed, Pelosi recently tried to scuttle that talk by saying she's not for impeachment, for now.
In a joint statement, Nadler, House intelligence committee chairman Adam Schiff, D, and House Oversight and Reform Committee Chairman Elijah Cummings, D, seemed to concede that collusion had not been found, saying they have confidence in Mueller, "notwithstanding the very public evidence of Trump campaign contact with and willingness to receive support from Russian agents."
Still, they said, "it will be vital for the country and the Congress to evaluate the full body of evidence collected by the Special Counsel, including all information gathered of a counterintelligence nature."
- AP
