Here are some of the 30 times Trump tweeted that China is a currency manipulator.— Brian Klaas (@brianklaas) April 13, 2017
"They're not currency manipulators."
The issue is complicated and can't be reduced to to simple pronouncements, which is why the currency manipulation charge worked for Trump during the campaign. Naming a foreign enemy and blaming them for your troubles is more viscerally 'persuasive' than articles like this.
The Transpacific Partnership is another example of a controversy that is largely beyond the understanding of most people, while lending itself to an Americans-versus-foreigners mentality so well that both Republicans and Democrats turned against it in the run up to the 2017 election.
None of this is intended to minimize the fact that many people feel ecomically screwed, but blaming foreign countries as a deflection is as old as the hills, and a favorite tactic of oppressive governments everywhere. It works for dictators and it works in liberal democracies under pressure. And not that a foreign entity can't be at fault, but it's psychologically easy to wrongly blame "them," especially if the subject is complex.