This is from the relevant section of the USMCA implementing legislation submitted to the House on Friday:
Subtitle B—Joint Reviews Regarding Extension of USMCA
SEC. 611. PARTICIPATION IN JOINT REVIEWS WITH CANADA AND MEXICO REGARDING EXTENSION OF THE TERM OF THE USMCA AND OTHER ACTION REGARDING THE USMCA.
(a) IN GENERAL.—Pursuant to the requirements of this section, the President shall consult with the appropriate congressional committees and stakeholders before each joint review, including consultation with respect to—
(1) any recommendation for action to be proposed at the review; and
(2) the decision whether or not to confirm that the United States wishes to extend the USMCA.
(b) CONSULTATIONS WITH CONGRESS AND STAKEHOLDERS.—
(1) PUBLICATION AND PUBLIC HEARING.—At least 270 days before a joint review commences, the Trade Representative shall publish in the Federal Register a notice regarding the joint review and shall, as soon as possible following such publication, provide opportunity for the presentation of views relating to the operation of the USMCA, including a public hearing.
(2) REPORT TO CONGRESS.—At least 180 days before a 6-year joint review under article 34.7 of the USMCA commences, the Trade Representative shall report to the appropriate congressional committees regarding—
(A) the assessment of the Trade Representative with respect to the operation of the USMCA;
(B) the precise recommendation for action to be proposed at the review and the position of the United States with respect to whether to extend the term of the USMCA;
(C) what, if any, prior efforts have been made to resolve any concern that underlies that recommendation or position; and
(D) the views of the advisory committees established under section 135 of the Trade Act of 1974 (19 U.S.C. 2155) regarding that recommendation or position.
...
(d) CONGRESSIONAL ENGAGEMENT AFTER JOINT REVIEW.—(1) IN GENERAL.—Not later than 20 days after the USMCA countries have met for a joint review, the Trade Representative shall brief the appropriate congressional committees regarding the positions expressed by the countries during the joint review and what, if any, actions were agreed to by the countries.
(2) CONTINUED ENGAGEMENT.—After a joint review, the Trade Representative shall keep the appropriate congressional committees timely apprised of any developments arising out of or related to the review.
I see lots of consultations with Congress and stakeholders in here, which is good. However, it seems like the ultimate decision on whether to extend the USMCA after 6 years is entirely in the hands of the executive branch. I think that's a mistake. If I were Congress, I would push hard for a stronger role. For example, the legislation could indicate that a decision not to extend could only be made if the president and a majority of both the House and Senate agreed.