WASHINGTON, July 2 -- The assembly line didn't change on Wednesday. But the legal architecture holding it together quietly did.

The United States declined to extend the Canada-United States-Mexico Agreement on July 1, the six-year review deadline built into the pact, triggering a 10-year expiry clock on a trade relationship that underpins $1.9 trillion in annual commerce and approximately $5 billion in daily cross-border transactions. U.S. Trade Representative Jamieson Greer confirmed the administration was not prepared to renew the agreement in its current form for another 16 years, in effect the first formal rupture in North American trade architecture since NAFTA entered force in 1994.

Trump had made his position clear weeks earlier....