Trudeau, 46, was leaving the Reagan Presidential Library where he had given a speech when a auto turned left in front of his motorcade on Friday, ABC News reported.
Trudeau was not injured, a Canadian government source said. And so is Mexico.
"The statements that have been coming out of the Philippines on the potential or possible uses of those helicopters have given us cause to need to follow up on that, and that's exactly what we're doing".
The prime minister, speaking in a building named for the president who signed the landmark Canada-U.S. free trade deal, conceded that the accord being renegotiated had to be updated to help people left behind by free trade and a technological revolution.
But he also acknowledged that global trade is not working for everyone and said income inequality is growing worldwide.
"We're going to continue to make an argument that it's not enough to just trade, we have to ensure that the benefits of trade are properly and fairly shared", he said.
The accord, he said, should be modernized with "a willingness to compromise on all sides".
Trudeau's stop in San Francisco highlights the already strong ties between Canada and California, particularly in research, academia and technology.
Trump called the 24-year-old NAFTA trade pact agreement a job-killing "disaster" on the campaign trail and has threatened to withdraw from it if he can't get what he wants. He has threatened to pull out unless the deal requires more auto production in the US, while shifting additional government contracts to USA companies.
Trudeau, who is on a four-day trip to the US, will travel about 40 miles to visit Los Angeles on Friday.
The sixth round of North Atlantic Free Trade Agreement (NAFTA) has ended in Montreal on Monday with a little "progress".
A weekend hike through Griffith Park marked the last public event for Trudeau on his four-day trip through the United States, where he hit communities that swung Democrat in the last presidential election to talk trade.
Earlier, Trudeau picked up promises of investments and jobs during his first official visit to San Francisco.
Trudeau spent Thursday pitching tech companies on investing in Canada while touting the country's fast-track visa for highly skilled workers.
Trudeau plans to meet with the presidents of eBay; Devin Wenig; Salesforce, Marc Benioff, and Amazon, Jeff Bezos.