[SpicyLemonZest]

I don't think the positions have reversed as much as you're thinking. Trump began this round of trade wars with a series of indefensible attacks on free trade with Canada, which is clearly good for American workers and has never been unpopular in the US. If Trump had done everything else he's doing here, but used a sensible formula and avoided pointlessly antagonizing Canada, you would see significant crossover support from the left.