20% tax would just increase the price of mexican imports. The consumers and buyers would be paying for the wall, not Mexico. To put into prespective, Texas alone imported around $84 billion from Mexico in the year 2015. With a 20% tax, Texas businesses and consumers would have paid an extra $16.8 billion for the same goods and services. Enough to pay the wall (supposedly) and thats a very possible final scenario.
Mexico is the main country when it comes to importing agricultural goods to the US, and considering how much the minimum wage is in Mexico and the variety of products that we receive, what we are paying to import those products (nearly nothing compared to other countries) replacing them as a business partner is going to improbable if not impossible. In 2015 US's imports from Mexico totaled $21 billion. Leading categories include: fresh vegetables ($4.8 billion), other fresh fruit ($4.3 billion), wine and beer ($2.7 billion), snack foods ($1.7 billion), and processed fruit & vegetables ($1.4 billion). the majority of it produced at 73.00 pesos per hour (about $4.30).
Earlier this week, a shipment of avocados from Jalisco, Mexico was stopped from coming to the US. Mexico turned around and sold the avocados to other countries at a 20% increase without a loss; meanwhile the prices of avocados in the US rose to 96.00 dlls a crate (the "normal" being 40.00 dlls a crate) Price increase, not enough product to meet the demand = consumers pay. The phrase "The guac will be extra" gets a new meaning.
To tax Mexico would mean to leave NAFTA for either country and to leave NAFTA would mean Mexico can also tax US products or increase the price of their own to cover losses. Its a two way, street. Thats why bullying one of your 3 main business partners is never a smart move.
Senator and sassy overlord Lindsey Graham had something to say (lol):