Eulogies from liberal and conservative figures alike, have been pouring in.
McCain stopped receiving cancer treatment earlier this week, his family saying "the progress of the disease and the inexorable advance of age render their verdict".
But in his address to the US Studies Centre previous year, Senator McCain did not shy away from conceding that Mr Trump was "unsettling" American allies, or that there is a debate underway in the United States about its role in the world, its resolution uncertain.
The late Arizona Republican, had organised his funeral, and close associates had told the White House in May that he did not want Trump to be invited.
McCain is welcomed by US President Richard Nixon on May 24, 1973, in Washington, following his release from captivity.
John Sidney McCain III had served as the senior senator from Arizona since 1987 and ran unsuccessfully against Barack Obama in 2008 on an ill-fated GOP ticket with vice presidential nominee Sarah Palin.
He began life in 1936 at a US naval base located next to the Panama Canal; the grandson of a four-star US Navy admiral and the son of a naval officer, who would also become an admiral.
"The thing about John McCain is that he was amazingly interested in the people around him", said Kaites, a former Arizona state legislator.
The president, who as a candidate in 2016 mocked McCain's capture in Vietnam, had jabbed at the ailing senator for voting against Republican efforts to roll back President Barack Obama's health care law.
Following the announcement of 81-year-old John McCain's death, the public took to social media to express their condolences and share mixed feelings about the Republican's life and deeds.
"Some lives are so vivid, it is hard to imagine them ended", Bush wrote. "I think it's unfortunate that he had people around him - and they continued to be around him for a very long time - who weren't serving him well".
Former President Bill Clinton and his wife, Hillary, said in a statement: "Senator John McCain believed that every citizen has a responsibility to make something of the freedoms given by our Constitution, and from his heroic service in the Navy to his 35 years in Congress, he lived by his creed every day".
Jon Biden, the former Vice President of the United States chose to highlight in his tribute what made Mr McCain overcome the many challenges that had characterised his life: country and spirit.
Justice Minister Ayelet Shaked eulogized the late United States senator John McCain on social media writing that "he was a true patriot and a true friend of Israel".
Arizona Governor Doug Ducey has released a statement describing McCain, who was elected to the US Senate from Arizona six times, as a "giant", an "icon" and an "American hero". "Canadians join Americans tonight in celebrating his life and mourning his passing".
McCain had been a rare and outspoken Republican critic of Trump, accusing him of "naivete", "egotism" and of sympathizing with autocrats.
Mr McCain's 2008 running mate said: "Today we lost an American original. Sen".
But John McCain was never afraid to reach across the aisle, so unafraid of straying from the party line that he earned the infamous Maverick nickname in the Senate. John never took the easy path in life - and through sacrifice and suffering he inspired others to serve something greater than self.
Trump's response: McCain was a "dummy" who had barely managed to graduate from the U.S. Naval Academy.
"Another anti-China warrior is down, godspeed, you can finally rest, there's no China in heaven", wrote one user on the Twitter-like Weibo.