Although he insisted he had a good relationship with Mr Justin Trudeau, just days after leaving in disarray a G-7 summit the Canadian prime minister had hosted, Mr Trump took another dig at him, saying the U.S. had a big trade deficit with Canada and that "a little balance" was needed.
The insults were supposedly a response to the post-G7 news conference in which Trudeau repeated his diplomatic criticism of Trump's steel and aluminum tariffs and said he would stand up for Canadians.
Normally a conciliatory, charming figure, Justin Trudeau is being forced to transform himself into a kind of "Captain Canada" in order to fight a trade war with Donald Trump that has the potential to be as destructive as it is surprising.
He called on Trudeau to apologise to Trump. For instance, Trump's steel and aluminum tariffs are expected to cause a drag on United States economic growth and result in a net loss of American jobs. He didn't specify what he considered false about Trudeau's statements.
Navarro's willingness to walk back his outburst marked a departure from the Trump administration's never-say-you're-sorry approach to political crises.
MPs force major soft Brexit shift
However, despite backing down, pro-Remain Tories signalled they would not be easily consoled by a compromise offered by ministers. It is thought that both the government and the Remainer group of Tory MPs consider the outcome to be a success.
However, the G7 summit was overshadowed by United States president Donald Trump's trade policy to impose tariffs on metals to EU, Canada and Mexico together with the fact that he left before the official climate talks begin showing his distinct stance to drop off the Paris agreement.
Kudlow's comments were quickly followed by Director of the White House National Trade Council Peter Navarr, who said there is a "special place in hell" reserved for anyone who double-crosses Trump.
As Canada teeters on the brink of a potential trade war with the United States, the Trudeau government has adopted the same motto invoked by the British as they braced for the Second World War: Keep calm and carry on.
He made the apology - something that former US ambassador to Canada Bruce Heyman, among others, was demanding that he do - during a Wall Street Journal event today in Washington. "Our Tariffs are in response to his of 270% on dairy!"
"I had a good relationship with Justin Trudeau, I really did".
That means Canadian stores shelves look a lot like United States shelves, and Canadians drink Starbucks while wearing Nikes, talking on their iPhones and munching Doritos.
And Roland Paris, a former foreign policy adviser to Trudeau, jabbed at Trump on Twitter: "Big tough guy once he's back on his airplane". Trudeau stuck our president in the back.
That's not a problem if you think we don't need allies, because they're all going to hell anyway.