Baker makes a good point about the rising trade effects on manufacturing from 2000 onward. However it seems like simply an acceleration of a longstanding trend. There is trade, and then there are trade agreements. Textiles, machine tools and sundry other industries were "running away" from the US long before Nafta, Cafta, Korean, or TPP trade deals. And there is very little corelation between trade flows and trade deals, worldwide, without assuming all sorts of "lags" in effect which, in the absence of much data, are just speculation. NO doubt we will learn more when UK exits the EU -- that will be a key test of what happens to trade when a market agreement ends.
So, Is Baker talking trade, or trade agreements? Not clear. Also, his args are a bit tongue in cheek -- he does not actually say that slowing either trade or trade agreements will "bring back" manufacturing. In order to know for sure if trade, or trade deals, either or both, are the "cause", and not just a correlated trend, with lost manufacturing jobs, we would have to stop both the trade and withdraw from the deals, and see if manufacturing returned....???? Very doubtful hypothesis.
Yes, Brad DeLong and some others are underplaying trade effects. But Baker may be in a cloud of "anti-trade" denialism himself.
Trade Denialism Continues: Trade Really Did Kill Manufacturing Jobs
-- via my feedly newsfeed