President Donald Trump's energy ambitions don't stop at U.S. borders.

His Venezuelan oil deal, under which the U.S. Department of Defense holds a 35% equity stake in a company that will develop 17 Venezuelan oilfields, is an effort to control energy resources in the Western Hemisphere. Under the agreement, the U.S. is guaranteed at least 20% of output from those fields "at production cost." In recent weeks, Trump has started saying the deal will give the U.S. access to 65 billion barrels of proven oil reserves in Venezuela.

Aside from the economic viability of those resources (many pieces would need to fall in place, from electricity grid repairs, to better governance and institutional capacity) and the doubtful legality of this ownership claim, the key question is why the U.S. is seeking ownership of overseas oil assets at all.

The U.S. is hardly short of oil and gas wealth. Its crude oil production, at nearly 14 million barrels a day, dwarfs Saudi Arabia and Russia's current output. In the U.S., oil-and-gas companies benefit from rule of law, stable contract terms, and unmatched access to capital markets and oilfield services providers. And if Trump's goal is to secure energy abundance in the Western Hemisphere, Canada deserves more recognition.

The U.S. imports more than four million b/d of crude oil from Canada, accounting for nearly two-thirds of its total imports. These volumes are especially critical in the Midwest, where refineries are configured to run Canadian heavy crude. Dozens of pipelines carry crude, petroleum products, natural gas, and natural gas liquids across the U.S.-Canadian border, as well as 86 international power lines. Bilateral energy trade last year amounted to $137 billion.

The economic benefits of this trade relationship are obvious: Integrated oil, gas, and electricity infrastructure maximize efficiency and lower costs for consumers.

Canada's limited export options and dependence on the U.S. market also translate to a pretty good deal on Canadian heavy crude. Western Canadian Select, a benchmark heavy sour crude, has traditionally sold at a steep discount to West Texas Intermediate crude. Energy analyst Rory Johnston notes that this enables the U.S. to import lower cost barrels and export higher value light sweet crude.

But, of course, this trade relationship is under fire. The U.S. trade deficit with Canada, largely due to a $111 billion energy trade imbalance, rankles Trump, who regards all deficits as signs of "losing" out to other countries.

Trump excluded energy from his 25% blanket import tariff on Canadian goods last year, as well as the additional 50% tariff he implemented this summer. Canadian energy that is compliant with U.S.-Mexico-Canada trade agreement rules remains tariff-free, though the administration has given reason to doubt the current terms of that agreement will remain as-is.

Canadians aren't pleased. Some Canadian officials have proposed retaliatory measures targeting energy exports. But, for now at least, it seems unlikely that the country will impose export duties. "I don't think they want us to stop sending any of that energy," Canadian Prime Minister Mark Carney said, before noting that Trump's tariffs are a "miscalculation."

Energy abundance and low energy costs are worthy policy goals, and perhaps new investment in Venezuela presages a more prosperous and better-governed industry that can help secure future supplies. But in an especially volatile period in global energy markets, the U.S.-Canada energy trade relationship is becoming increasingly valuable. It would be wise to protect it.

Guest commentaries like this one are written by authors outside the Barron's newsroom. They reflect the perspective and opinions of the authors. Submit feedback and commentary pitches to ideas@barrons.com.

Ben Cahill is a nonresident senior fellow at the Atlantic Council.