So far this year, through the end of April, the United States has exported 3.37 million tons of steel, a 2.5 percent decrease. About 1.73 million tons were shipped north to Canada, a 2.7 percent increase, but exports to Mexico were down by more than 10 percent; exports to the European union were up 20 percent year over year.

In April, exports to Canada rose 2 percent year-over-year to 443,231 tons, and exports to Mexico shot up to 9.2 percent as compared to March to 323,687 tons, according to the AIIS. Exports to the European Union skyrocketed by 30 percent to 33,571 tons in April.

"Steel exports will likely be one of the first areas where the harsh consequences of the increased trade-related conflict with our NAFTA partners will be seen," American Institute for International Steel President Richard Chriss said in a press release.

"The administration’s deconstruction of NAFTA, creating what the Wall Street Journal termed 'a looming NAFTA debacle,' its decision not to exempt Canada and Mexico from its ill-advised 25 percent steel tariffs, and the unnecessary stresses placed on hemispheric and trans-Atlantic concord as a result of the just-concluded, poorly planned G7 Summit, will likely roil trade relations even more, and result in retaliation by the two biggest purchasers of American steel, driving down exports from the United States."

Steel imports in the United States dwarf steel exports. While the U.S. steel mills exported 3.37 million tons of steel through the end of April, the country imported 12.4 million tons of foreign-made steel during that same period, according to the American Iron and Steel Institute.