New Delhi, March 16 -- Every day more than $4 billion worth of goods cross the United States' borders with Canada and Mexico - U.S. auto parts headed for car factories in northern Mexico, cartons of Mexican avocados bound for California supermarkets, Canadian aluminum destined to become cans of Campbell Soup.

Much of this bustling cross-border commerce is duty-free, thanks to the US-Mexico-Canada Agreement, or USMCA, that President Donald Trump negotiated with America's northern and southern neighbors during his first term.

But the future of the USMCA , which took effect July 1, 2020, is cloudy as the three countries begin what could be a tempestuous attempt to renew the pact this year. The United States is demanding changes to the trea...