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."If countries will not make fair deals with us, they will be 'Tariffed!'" he tweeted Monday.China was in his sights at the start of . . .