The U.S. Department of Commerce completed its Section 232 investigations and sent reports to the President concluding that steel and aluminum imports threatened to impair U.S. national security. These findings created the legal basis for the President to impose trade restrictions such as tariffs or quotas.
President Trump issued proclamations under Section 232 to apply a 25% tariff on steel and a 10% tariff on aluminum from most countries. The measures were framed as national-security actions and became a major new source of trade friction with U.S. partners, including NAFTA countries.
The 25% steel tariff and 10% aluminum tariff began applying to covered imports, with some temporary country exemptions still in place at first. This start date matters because it triggered compliance changes at the border and started reshaping North American supply-chain costs.
The United States extended (but did not make permanent) exemptions for Canada and Mexico from the Section 232 steel tariff until the end of May 2018. This made the North American situation especially uncertain, since NAFTA renegotiations were also underway.
After the exemption period ended, Section 232 tariffs began applying to steel and aluminum imports from Canada and Mexico. This escalated trade tensions inside North America and quickly led to retaliation plans by both countries.
Mexico published a list of retaliatory tariffs covering U.S. farm and industrial products (including pork, apples, and some steel items) in response to the U.S. Section 232 measures. The retaliation increased political pressure inside all three NAFTA countries because it targeted visible products and sectors.
The European Union adopted “rebalancing” duties on selected U.S. imports in response to the U.S. steel and aluminum tariffs. Although not a NAFTA action, the EU response showed that Section 232 was creating broad international resistance, complicating U.S. efforts to manage multiple trade relationships at once.
Canada imposed surtaxes on U.S. steel, aluminum, and other products totaling C$16.6 billion, matching the scale of trade affected by the U.S. measures. The Canadian action intensified pressure for a negotiated solution because it affected many consumer and industrial goods moving across the U.S.–Canada border.
The United States, Mexico, and Canada signed the USMCA to replace NAFTA, but the Section 232 steel and aluminum tariffs and related retaliation remained major obstacles to smooth ratification. The metals dispute became tightly linked to the politics of approving the new agreement.
The United States agreed with Canada and Mexico to remove Section 232 steel and aluminum tariffs on their exports, and both partners agreed to remove their retaliatory tariffs. This step reduced a major barrier to USMCA ratification and reset the trade relationship toward implementation of the new agreement.
The three countries signed a Protocol of Amendment to modify the USMCA, reflecting negotiations aimed at winning legislative support (especially in the U.S. Congress). This helped clear a path for final passage while the metals tariffs issue had been eased by the May 2019 deal.
After congressional votes in late 2019 and early 2020, the USMCA implementation act was signed into U.S. law. This created the domestic legal framework needed for the United States to bring the agreement into force and formally replace NAFTA.
The USMCA entered into force, officially replacing NAFTA and setting updated rules for North American trade. In the Section 232 context, the timeline closed with a new regional baseline: the metals tariffs and retaliation that had disrupted NAFTA-era trade were removed for Canada and Mexico by 2019, and North American trade governance shifted to the USMCA framework in 2020.
Section 232 Steel & Aluminum Tariffs and NAFTA/USMCA Trade Responses (2018–2020)