And since the European Union and other trading partners have indicated they intend to retaliate or challenge the move at the World Trade Organization, industries that will be the target of retaliation, such as bourbon and agriculture, will join steel users in lobbying for restraint, said Joel Trachtman, a professor at the Fletcher School of Law and Diplomacy at Tufts University.
Yerxa said, "If the U.S. can claim that steel is a national security issue, certainly other countries can claim that autos is a national security issue." He noted that U.S. auto plants exported about 2 million vehicles last year.
Steel and aluminum tariffs could also lead to congressional pushback, given the economic threat to state and local economies from higher raw-material prices. Many members of Congress were frustrated by the tariffs on solar panels and washers, and afterward, several of them expressed interest in exploring options to rein in the president's authority to carry out trade policy.
There is also a groundswell of support for the North American Free Trade Agreement on Capitol Hill as members realize how many jobs are tied to trade with Canada and Mexico. The U.S. is also negotiating with Korea to amend a bilateral trade agreement to address the U.S. trade deficit, primarily in autos.
The steel tariffs don't bode well for NAFTA or the Korea agreement because other parties will perceive the U.S. as having taken unilateral action while they try to negotiate in good faith, several trade experts said. Canada, Mexico and Korea are large steel exporters to the U.S.
"We're basically sticking our finger in their eye, so that's going to make them less likely to make painful concessions to us," Yerxa said.
Jerry Dias, head of the Canadian auto union Unifor and a consultant to the Canadian negotiating team, told Reuters last week that the steel announcement had soured the mood and dashed hopes for a breakthrough in NAFTA talks. "It is crystal clear to us that if Canada is not exempted from the U.S. tariffs," he said, "then Canada should walk away from the NAFTA table."
The broader problem, said Yerxa, is that the U.S. is isolating itself, while the European Union, Canada, Japan, Mexico and other nations are cutting trade agreements with one another.
Car companies that want to sell finished vehicles to Europe, for example, might look more favorably on shifting final assembly to Mexico or Japan rather than having to pay the 10 percent tariff on steel imported to the U.S.
"We're going to be on the outside of their tariff walls," Yerxa said. "And pretty soon it is going to be the U.S. that is the least favored nation in these major trade relations. And that is really bad for the auto industry."