I believe what he is referencing is the trade deal USMCA.
It has to be put into a legislative format and then sent to the House/Senate to be ratified.
Just because US/MX/CA have agreed to it - our legislative bodies must approve of it.
There are certain rules regarding these that must be followed.
Once the President notifies congress the process must play out.
[United States
Treaty power is a co-ordinated effort between the Executive branch and the Senate. The President may form and negotiate, but the treaty must be advised and consented to by a two-thirds vote in the Senate. Only after the Senate approves the treaty can the President ratify it. Once it is ratified, it becomes binding on all the states under the Supremacy Clause. While the House of Representatives does not vote on it at all, the requirement for the Senate's advice and consent to ratification makes it considerably more difficult to rally enough political support for international treaties. Also, if implementation of the treaty requires the expenditure of funds, the House of Representatives may be able to block or at least impede such implementation by refusing to vote for the appropriation of the necessary funds.
The President usually submits a treaty to the Senate Foreign Relations Committee (SFRC) along with an accompanying resolution of ratification or accession. If the treaty and resolution receive favorable committee consideration (a committee vote in favor of ratification or accession), the treaty is then forwarded to the floor of the full Senate for such a vote. The treaty or legislation does not apply until it has been ratified. A multilateral agreement may provide that it will take effect upon its ratification by less than all of the signatories.[4] Even though such a treaty takes effect, it does not apply to signatories that have not ratified it. Accession has the same legal effect as ratification, for treaties already negotiated and signed by other states.[5] An example of a treaty to which the Senate did not advise and consent to ratification is the Treaty of Versailles, which failed to garner support because of the Covenant of the League of Nations.
The US can also enter into international agreements by way of executive agreements. They are not made under the Treaty Clause and do not require ratification of two thirds of the Senate. Congressional-executive agreements are passed by a majority of both houses of Congress as a regular law. If the agreement is completely within the President's constitutional powers, it can be made by the President alone without Congressional approval, but it will have the force of an executive order and can be unilaterally revoked by a future President. All types of agreements are treated internationally as "treaties". See Foreign policy of the United States#Law. ]
From Wikipedia, but it's concise.
https://en.wikipedia.org/wiki/Ratification