In the days leading up to the summit, Trudeau and Macron have severely criticized Trump's new tariffs, which critics say threaten to drive up prices for American consumers and companies and heighten uncertainty for businesses and investors around the globe.
Trump's reversal, announced while he was en route to Singapore for a meeting with North Korean leader Kim Jong-un, sent his G-7 partners scrambling.
The president has accused Canada of taking advantage of American workers through their trade practices. "We must put the American workers first!"
The communique, which had appeared to have papered over the cracks that surfaced so uncharacteristically at the G7, said the leaders of the United States, Canada, Britain, France, Italy, Germany and Japan were agreed on the need for "free, fair, and mutually beneficial trade" and the importance of fighting protectionism. And what did Trudeau do as soon as the plane took off from Canadian airspace? On Saturday, Trump warned that "if they retaliate, they're making a big mistake".
Mr Trump said the United States paid "close to the entire cost of Nato" to help protect countries that "rip us off on trade".
Media captionWho left their mark on President Trump at the G7 summit?
He said he believes other countries are now more committed to a fairer trade relationship. "These are really unrelated baskets of issues".
Donald Trump has taken a fresh swipe at key allies after a war of words broke out following the United States president's decision not to endorse the conclusions of a G7 summit.
The U.S. president's reception in the picturesque town of La Malbaie along the St. Lawrence River is set to be a far cry from when Ronald Reagan visited Quebec three decades ago, when he was so friendly with Prime Minister Brian Mulroney they sang a song together.
The G7 communique references a number of shared priorities, including on trade, economic growth, national security and sustainability.More news: LeBron James free agency: When will Cavs star reveal his decision?
Tariffs, a major point of contention, were taken on in the statement, though in more diplomatic terms than the earlier back-and-forth between Canada and the U.S.
He again suggested the United States was footing too much of the costs of North Atlantic Treaty Organisation and "protecting many of these same countries that rip us off" on trade.
"The European Union had a $151 Billion Surplus-should pay much more for Military!"
"They pay only a fraction of the cost - and laugh", he wrote, adding that the European Union needed to pay "much more" to help fund the worldwide military alliance, which comprises of 28 members including the UK, US, Germany, Canada and Turkey.
In Paris, Macron's office said it wouldn't make sense and pointed out that the latest country to impose economic sanctions on Russian Federation was the U.S. Italy's new premier, Giuseppe Conte, tweeted that he agreed with Trump, saying: "Russia should go back into the G-8".
Mr Trump went on to say that the U.S. gets "unfairly clobbered" on trade despite "protecting Europe at great financial loss".
The majority of Canadian exports go to the United States, making Canada uniquely vulnerable to a U.S. trade war.
Trump fired back after Trudeau's press conference, blasting the Canadian leader on Twitter as "very dishonest and weak".
"There's a special place in hell for any foreign leader that engages in bad-faith diplomacy with President Donald J. Trump and then tries to stab him in the back on the way out the door", Navarro said on Fox News Sunday.
"This year's G7 meeting is already going down as the G6 + 1, with six members on one side and President Trump on the other", Al Jazeera's John Hendren, reporting from Quebec, said.