The problem is how to do so without also impacting transfer payments to subsidiary companies based in Mexico to keep supply chains functioning. I would imagine that might be a big part of the 'significant piece of Mexico's economy' referred to, possibly more-so than the 'illegal immigrants sending their ill begotten money back home to stuff under their mattresses' sort of nonsense that people use to make this all seem like an exercise in 'squaring the scales of justice.'
With the "just in time" business model of far-flung supply chains, it won't be long before downstream U.S. workers are laid off, then more overhead/office types when inventory empties and sales drop off a cliff.