Trudeau was in California giving an address touting the benefits of the North American Free Trade deal and met with Garcetti this morning for a media event and a hike.
California sells some $25.4 billion in goods and services to Canada, and nearly 1.2 million jobs in the state rely on trade, according to federal statistics.
The location is a symbolic choice, referring to the longstanding trade relationship between the US and Canada.
His remarks at the Ronald Reagan Presidential Library in Simi Valley, California, struck a cooperative tone at a time when President Donald Trump is threatening to withdraw from the 24-year-old pact that governs trade on the continent.
"That would harm the very folks who need our help most".
The next round of NAFTA negotiations faces multiple sticking points that negotiators hope to sort out before the twin disruptions of a presidential election in Mexico and USA congressional midterms.
Behind Trudeau, a cloudy California sky obscured the city's most famous message: the Hollywood Sign. In Chicago, he suggested that ending that trade would cause economic disruption that could hurt Trump politically. The three sides must still figure out rules around autos, a sunset clause and an mechanism to resolve disputes between countries and investors.
While much of the attention on NAFTA has focused on physical commodities such as vehicle manufacturing, dairy and timber, skilled workers have also become increasingly mobile between the U.S., Canada and Mexico.
Trudeau said there is a downside to the rosy trade picture he drew.
A speech in which Trudeau evokes Reagan could force Republicans who lionize the former president to reconcile abandoning one of their hero's key accomplishments, Speer said.
"If we make the political heat too hot for the president, maybe he'll make a decision that would enable us to stay in". "This isn't Canadian weather", Trudeau responded.
The Canadian prime minister came with an unambiguous message on his latest United States visit: the North American Free Trade Agreement needs to be modernised, not abandoned. A copy of the agreement, along with a Reagan autograph, were presented to Trudeau ahead of his speech.
Trudeau even said that if NAFTA is a bad idea then there is no good idea either. Trudeau said his father, former prime minister Pierre Trudeau, had a more nuanced relationship with Reagan, but one that was no less constructive - similar to the younger Trudeau's relationship with Trump.
Trudeau has said Trump should not snap the ties just for the sake of "winning".
For more than two years, US President Trump criticised the agreement and also hinted to take some serious steps being in the administration or at least send some ultimatums.