U.S. President Donald Trump appears to have a fondness for threatening countries with tariffs if they refuse to sign trade deals he likes. (Kevin Lamarque/Reuters) Canada maintains that its efforts to evade American tariffs on steel and aluminum, and threatened tariffs on cars, are on a "separate track" from the ongoing NAFTA talks.But that's not how U.S. President Donald Trump sees it. His attempts to use tariffs as leverage in NAFTA negotiations have become such a ingrained habit by this point, he's started using the word as a verb . . .