Who Will Be Affected?

Steel and aluminum workers could be hit by tariffs. For now, the broader economy probably will not.

Australia exported about 500 million Australian dollars ($400 million) of aluminum and steel to the United States last year. That totals only about 5 percent of Australia’s American-bound exports. By contrast, Australian meat exports to the United States are roughly five times that size, according to IHS Global Trade Atlas, a data provider.

In fact, Australia’s largest steel maker was initially seen as a potential winner. Shares of Bluescope Steel jumped last week after Mr. Trump vowed to impose tariffs because it has operations in the United States. Investors saw the possibility that the company’s American arm could charge more for what it makes.

The bigger hazard for the Australian steel industry is that American tariffs will force steel makers in other countries to send more of what they make to Australia. That could result in leaner profits, price wars and local layoffs.

“If the exports get the tariffs whacked on them, we’re going to have surplus of steel and aluminum in the marketplace — and at the same time as the rest of the world is,” said Daniel Walton, national secretary for the Australian Works’ Union, one of the country’s largest blue-collar unions.

Could It Get Worse?

It could, if steel and aluminum tariffs lead to something more drastic.

Canadian and European officials have already publicly discussed ways they could retaliate. United States trading partners could specifically target products made in parts of the country that support Mr. Trump, such as soybeans from the Midwest and bourbon from Kentucky.