Oil and vehicles are by far the two most important exports from Canada to the United States, accounting for more than 40 percent of movement across the border.

Companies like GM, Fiat Chrysler, Ford, Honda and Toyota all have assembly plants in Canada. About $58 billion in cars and car parts came from Canada last year, compared to $74 billion from Mexico. While Mexican light vehicle production has exceeded Canadian production since 2008, both grew at a higher rate last year than production in the United States.

“While it is a well-publicized fact that Mexico’s domestic consumption is less than 20 percent of the vehicles it manufactures, Mexico is not North America’s only export powerhouse,” wrote the authors of a recent report by the Michigan-based industry group Center for Automotive Research. “Canada is even more dependent on exporting outside its own borders, with domestic consumption of just 12 percent of the vehicles it manufactures within its borders.”

Changes to the fee-free exports could hit companies hard. About 80 percent of Toyotas produced in Canada are exported to the U.S., executives said in a recent earnings call.

But the United States is still by far the biggest vehicle manufacturer of the three, according to data from the international car manufacturing organizations OICA. And U.S. producers have become reliant on a trade system that allows parts to pass over the border multiple times during assembly. That’s why a list of exports from the U.S. to Canada doesn’t look very different from the import list.

Canada is also both a major importer and exporter of crude oil. While Canada produces nearly 5 million barrels of crude a day, that oil is coming from Western Canada and is difficult to transport to Eastern Canadian markets, according to government reports. Still, Canada exports to the U.S. about three times as much fuels and oil as it imports. Both measures have taken a hit in the last year as oil prices have remained relatively low.

Any import tax would likely increase gas prices in the U.S., but it could also move more investment into U.S. oil fields. Prices on other commodities, like natural gas, lumber and beef would also be expected to rise, at least in the short term.

Changes to the trade agreement would likely affect smaller industries too: Top import categories include breads, pastries and empty medicine capsules; chemical and mineral fertilizers; and tires. Canadian chocolatiers have been growing of late, increasing exports to the U.S. by more than 25 percent in the past two years.

NAFTA has also provided both the U.S. and Canada access to a larger pool of employees, including Canadians working in the U.S. on NAFTA visas.

Overall, Canada is the third-largest exporter of goods to the United States, but it’s America’s largest export market. It depends on the U.S. for expensive manufactured items like those in the export chart above, but also for billions in agricultural goods like fresh fruit and vegetables, according to the Office of the United States Trade Representative.

Canadians invested about $261 billion in the United States in 2014 — up 11 percent from 2013. Foreign direct investment could suffer if new policies make the border more restrictive. U.S. companies that sell services in Canada could be affected as well, as American companies export far more services than Canadian firms sell in the U.S.

Canada’s proximity to the U.S. could help its economy in other ways, if the U.S. enacts other isolationist policies proposed by the Trump administration. Canadian cities are already lining up to be the next destination for tech firms looking to hire international workers who are no longer able to work in the U.S., for example.