All good points except we have run a current accounts deficit (goods and services) with Mexico since 1995, I believe that is what the President’s tweet was referring to… not Mexico’s overall trade imbalance.
The confusion is understandable, for my letter is distressingly unclear, but the point of my letter remains valid. Here’s my (slightly edited) reply, on Facebook, to Mr. Foster:
Yes, but Trump’s tweet implies that Mexico’s bilateral trade surplus with the U.S. is a source of net profits for Mexico. Especially in a world with more than two countries, this implication is simply mistaken. It makes no more sense than, say, Trump observing that McDonald’s has a trade surplus with Trump and then concluding from this fact that McDonald’s trade either with Trump, or in general, is necessarily profitable.