I'm desperately trying to find a silver lining in a Trump presidency. He's already divided America by playing to racial divisions, threatened to amplify climate change as much as possible, talked about how much he loves illegal torture and murdering the civilian families of suspected enemy combatants, blatantly disregarded the US Constitution with a proposed ban on a specific religion, and betrayed his own campaign rhetoric about cleaning up Washington insider politics by hiring the dirtiest Washington insiders he can find.
But what about the wall? Lots of people here have voiced support of a physical barrier on the southern US border as both a literal way to divide people further and a symbolic expression of their desire to keep immigrants out of the country. I think it's a dumb idea, physically impractical to build, enormously costly to maintain, and totally ineffective at reducing illegal immigration.
With that said, I'm still trying to find any hint of honesty in his proposals and policies, and I think I know how to make Mexico pay for this particular horrible idea. The Mexican federal government will never write Uncle Sam a check, of course, but we can probably find ways to force Mexico to incur costs that America currently covers, just because we are big and powerful and they are not, and the powerful can always bully the weak.
For example, there is significant cooperation between US and Mexican border patrol forces. When we capture illegal immigrants coming across the southern border, we process them and lock them up in detention facilities while we figure out where to send them. This costs us money, regardless of what country the immigrants come from. These people came to America seeking freedom and opportunity, or fled from violence and oppression in their home countries, but we don't need to offer them an expensive prison cell. We could instead institute an 8 hour window for transport back across the Mexican border. Just open the gate and shove those little kids through, turning them all loose in the same city block in Juarez. No paperwork, no detention, just a taxi ride by armed federal agents. Mexico would have to figure out what to do with them, which in practice is probably to hope they disappear into the slums before trying to cross the border again.
How else could we penalize Mexico in the name of "paying for the wall"? The US currently spends several hundred million dollars per year on the Merida Initiative, a cooperative international crime-fighting plan designed to combat drug cartels. We help Mexico go after drug kingpins, we seize cartel financial assets, we fight against corruption in the Mexican government that lets drug cartels buy their way out of trouble. We fly aircraft along the border looking for drug smugglers. All of that could stop, and Trump could claim he was "transferring those costs" to Mexico. In reality, Mexico can't do any of that on its own and we would just be making the border drug war worse, not better. But Trump could say he was "making Mexico pay for the wall" by reducing US expenditures on border security, and this would seem to be right in line with much of the rest of his policy initiatives. Ignorance is Strength, sayeth Big Brother.
Let's see, those two things don't nearly cover the cost of the wall all by themselves. How else can we we make Mexico pay? We currently send money to the UN as part of our international nonproliferation efforts, to slow the spread of nuclear weapons. Mexico is a partner in those efforts. We could stop funding those programs at the UN, and say it was because they were a benefit to Mexico that Trump is taking back to help pay for the wall. The result would be more nukes in more countries, but hey at least we'd have that big beautiful wall to keep us safe.
What about trade? NAFTA removed most tariffs on goods made in Mexico, so repealing it would allow Trump to slap a 50% tax on everything crossing the border. That's a YUGE amount of money to help pay for wall! Of course, most of these goods are assembled in Mexico by US companies who moved their factories there to avoid paying for US environmental and worker protection laws, so this is effectively a new business tax on US corporations but I don't think that would stop Trump from saying he was "making Mexico pay". It also overlooks the reciprocal tariffs that Mexico would restore on US goods, which could be ANOTHER 50% tax on US corporations. Trade liberalization was a huge benefit to capitalism in all three countries, and returning to the age of protectionist trade policies doesn't really make any sense in the modern global economy, the way it might have after WWII when the US had most of the world's remaining intact manufacturing capacity.
NAFTA is a complicated topic with lots of provisions, but after 25 years the net impact has been undeniably positive for US corporations, and arguably negative for US workers. With only slight rhetorical gymnastics, I think Trump could claim that penalizing US companies who use robots to assemble cars in Mexico was all part of his plan to "make Mexico pay for the wall."
So to summarize: reduce border enforcement, stop fighting the drug cartels, abandon nonproliferation efforts, and tax US corporations. That should just about cover the cost of a new wall, which won't keep out illegal immigrants, won't stop the flow of drugs, won't make us more secure, and will cost US businesses money, all in the name of making Mexico pay for it.