He blamed past world leaders, including past presidents, for that situation, but said the current crew - including Prime Minister Justin Trudeau - now know that the "gig is up".
Trump said on Twitter that he would not sign the communique, calling Trudeau "very dishonest & weak" for his trade criticism.
The comments, made after Trump had left to go to Singapore for his much-anticipated meeting with North Korean leader Kim Jong Un, infuriated the USA president.
"POTUS is not going to let a Canadian prime minister push him around on the eve of this", Kudlow said, using an acronym for president of the United States.
Canadian Prime Minister Justin Trudeau said earlier that all countries attending the Group of Seven summit have signed a joint communique despite sharp trade tensions with the U.S.
White House aide Larry Kudlow tells CNN's "State of the Union" says Trudeau has done a "great disservice" to the G-7 by saying Canada had to stand up for itself and that the US was responsible for the problem with tariffs.
President Donald Trump wrapped his short trip to Canada extolling his relationship with the G7 countries as a 10 out of 10, and blasting reports of rifts between the USA and world as nothing more than "fake news".
But Trudeau says what the leaders did this weekend was "roll up our sleeves" and figure out language they could agree to on a broad range of issues.
On Friday, European Council President Donald Tusk said Trump's criticism of the worldwide rules-based order is "playing into the hands of those who seek a new post-West order where liberal democracy and fundamental freedoms would cease to exist".
Donald Trump and Justin Trudeau have been at loggerheads over trade tariffs
"He is not going to permit any show of weakness on the trip to negotiate with North Korea".
He said Trump "did the courtesy to Justin Trudeau to travel up to Quebec for that summit".
Navarro calls that a "socialist communique" that Trump pulled out of. From promoting democracy and to fighting terrorism, "we're on the same page".
Even a boilerplate communiqué, which reiterated the rich nations' commitment to free and fair trade, was undermined at the last minute, when American president Donald Trump repudiated the agreement.
He described Trudeau's actions after the G7 summit as a "sophomoric play".
"It's a betrayal, essentially a double-crossing", Kudlow said.
Mr Trump, who was leaving the summit in La Malbaie early, told reporters the United States needed protectionist tariffs because "we are like the piggy bank that everyone is robbing". John McCain and ex-FBI director James Comey - who Trump unceremoniously fired previous year - took to Twitter to offer their support.
Kudlow also accused Trudeau of trying to undermine the US president at a critical time before his summit with the reclusive Kim on Tuesday. Re-admitting Russian Federation to the group would be an "asset", according to the president. "It's for them that we work together. Canada, thank you for the flawless organization of G7!"
Netanyahu Warns Assad On Iranian Presence In Syria
I am very fruitfully cooperated with the American presidents with those with whom I agree and those with whom I was not. May said. "We will remain committed to it as long as Iran meets its obligations.
McCain to allies: 'Americans stand with you, even if our president doesn't'
May reiterated the need to avoid tit-for-tat actions in a trade dispute between the European Union and the United States. Trump did smile and wave with the other leaders at the traditional posed "family photo", on a bluff high above the St.
Trump signals willingness to back bill easing pot regulation
Cory Gardner and Elizabeth Warren . "I know exactly what he's doing", Trump said of Gardner and Warren's, bill. Nine states have now legalized recreational marijuana and 29 others have legalized it for medical purposes.