With all the controversies over the US imposing tariffs on steel and aluminum (discussed here and here, for example), it's perhaps useful to consider an overview of what import restraints the US economy already has in place, and what effects they have had. Every three or four years, the US International Trade Commission publishes a report called: “The Economic Effects of Significant U.S. Import Restraints.” TheNinth Update came out in September 2017.  The report notes: 

“[T]he United States is one of the world's most open economies. The average U.S. tariff on all goods was 1.5 percent (based on trade-weighted import values) in 2015. As tariffs fall and trade expands, households of all income levels benefit from lower-priced imports. A major part of the growth in global trade is due to the increased use of global supply chains, in which parts of the production process are completed in different countries. …

“The U.S. International Trade Commission (USITC or Commission) estimates that the net change to total U.S. economic welfare from removing significant U.S. import restraints would be a positive one—an average annual increase of about $3.3 billion during 2015–20.  … Among agricultural products, the restraints that currently restrict trade the most are those applied to sugar. Among manufactured goods, the most restrictive restraints are in the textile and apparel industries and in leather and allied product manufacturing, which includes footwear … The largest effects from the removal of significant import restraints are in the textiles and apparel sector, where consumers would benefit from lower-priced imports and where net U.S. welfare would increase by $2.4 billion. …

“The report divides all U.S. households into 10 groups, based on their income level, and
estimates the effects of removing significant U.S. import restraints on each group. A typical annual household consumption basket would cost from $54 to $288 less each year if significant import restraints were removed, depending on the household group. Higher income groups benefit more than lower ones in dollar terms because they spend more; as a share of income, all income groups benefit by about the same percentage.

“When an import restraint is removed, the U.S. price of that import declines. Producers making similar products reduce their prices to compete better, and some may shut down, thus decreasing domestically produced supply and displacing workers. Over the long run, displaced workers will likely move to jobs in other sectors, and business owners will likely invest in other, more profitable sectors. The costs to displaced workers include temporary job loss, possible lower wages in new jobs, and the costs of transitioning from one job to another. The most efficient firms will continue to produce, improving the overall efficiency of the industry, and those firms will likely increase exports. Consumers, including producers who use imports as inputs, gain from the lower prices
on imports and competing U.S.-produced goods. In total, the gains typically outweigh the costs, although some households, sectors, and regions may be harmed.”