Canada, Mexico and E.U. leaders vow to retaliate for U.S. tariffs Some of America's closest allies are fighting back after the Trump administration hit Europe, Mexico and Canada with new tariffs. Starting today, the U.S. will place a 25 percent tariff on imported steel and a 10 percent tariff on aluminum. Leaders from the countries say they'll retaliate with tariffs on some American exports. Ed O'Keefe reports.