This will tell you who Trump will target;
https://ustr.gov/countries-regions/americas/mexico
The US has been running a Goods trade deficit for quite some time. They do run a services surplus though. It makes sense a goal would be to balance that. I'm pretty sure the Americans don't have an appetite for an increase of 20% on most of their consumer items. Which is what will happen if Trump declares import tax on the countries who are taking advantage of American consumerism (China, Japan, Mexico, Germany).
edit; probably put this in the wrong thread.