But if there's anyone to blame for Trump coming back from Quebec looking weak, it isn't Justin Trudeau.
And while it may be that Trump could never have entered the summit with North Korea in a position of real strength, he certainly isn't doing that now.
That's true for a number of reasons, but what they all come down to is that Trump is the one more eager for an agreement, and Kim knows it.
The US has already given Kim something very valuable: the summit itself.
Standing next to the leader of the world's most important power gives Kim a prestige and status that his father and grandfather both wanted but couldn't get, because American presidents were unwilling to offer it.
In that way, the summit has already been a victory for Kim, and it will be a victory even if no agreement is reached.
Perhaps most importantly, the US is asking Kim for something very big, something America wants very much, and something he is disinclined to give.
The US finds the status quo - with North Korea in possession of nuclear weapons and the means to deliver them almost anywhere - unacceptable, while Kim finds the status quo tolerable, even granting his country's awful economic situation.
That means that unless he really believes the US is going to launch an attack on his country (which is highly unlikely) he's in a position to walk away while the US will have to keep offering him more and more in exchange for giving up his nukes.
Trump, furthermore, has been publicly itching for an agreement, which puts him in a position of weakness, and this shows what a different situation he is in from the ones he faced as a real estate developer.
One thing Trump often did in negotiations as a businessman was threaten to walk away, which he could do precisely because he was often in a position of strength.
If you're negotiating with a vendor who's going to sell you some gold-plated bathroom fixtures or a bunch of pianos, you can use your ability to abandon the negotiations because both you and the vendor know you can go elsewhere if you don't get what you want. That allows you to keep driving the price down to the absolute minimum the other side will accept.
But there are no other nuclear-armed boy dictators for Trump to negotiate with.
He can't just walk away.
And he has made it clear how eager he is to reach an agreement on North Korea's nuclear weapons, even throwing around the idea of him winning the Nobel Peace Prize. Kim knows this well.
It gets worse.
The disaster of the G7 summit, in which Trump acted like a petulant child with the other leaders and then had a tantrum afterward, has only put him in a weaker position, as Richard Haass of the Council on Foreign Relations tweeted:
"The unravelling of G7 summit works in NK's favour as @realDonaldTrump will not want to bust up 2 summits in a row lest people conclude he is the problem. Increases incentive for Kim to up his asks and limit his compromises and for Trump to do the opposite. Hardly the ideal context"
A different president might be able to put aside questions of his momentary political standing and how failure would make him look, and just focus on the task at hand. But Trump is not that president. Everything is personal with him, as we well know.
Trump is also ignorant and impulsive - which the North Koreans no doubt understand.
Who knows what he'd be willing to accept from them or give up in exchange, if he didn't really grasp what he was doing.
And more than any other president, he's likely to ignore the pleading of his aides if he's about to make a terrible deal, in no small part because of his boundless faith in his own ability to understand people.
"I think within the first minute I'll know" whether Kim is serious about denuclearisation," he said. "Just my touch, my feel. That's what I do."
That is utterly ludicrous, and it suggests that Trump will be easy to bamboozle.
We're past the point where anyone honestly believes the President is a great negotiator, or even a good one.
This may partly explain why his aides have been trying to lower expectations for this summit, portraying it as just the first step in a lengthy process.
Which may mean that in the end it winds up like the negotiations previous administrations had with North Korea: extended, frustrating, and marked by moments of hope followed by years of disappointment.
It would be wonderful if Trump could achieve a meaningful breakthrough that leads to the dismantling of Kim's nuclear arsenal. But it's hard to see how he'll be able to make it happen.
