It’s not just “Remain in Mexico” that would die. Bilateral cooperation between law enforcement agencies would go the way of the dodo, making future operations almost impossible. Mexico is America’s largest trading partner. If either side were to shut down legal ports of entry to traffic (the way Texas Governor Greg Abbott did), it would have major economic impacts, and the other side would likely retaliate in kind. And the worst part is, experts who have looked at this don’t believe the strikes would significantly impact the flow of drugs.
This gets even worse if the U.S. starts to summarily execute people who are suspected (or found to be) smuggling drugs, in great part because almost none of what the GOP base believes about smuggling (or what their presidential candidates tell them) is true. Over 90 percent of fentanyl is seized at legal ports of entry and not between them. Almost all of it is found on people who have a legal right to enter (e.g. U.S. citizens), and almost none of it is found on migrants looking to find work or on asylum seekers. Most of the fentanyl that penetrates our borders is carried by individuals or hidden in passenger vehicles, though some is concealed inside tractor-trailers carrying loads of legitimate cargo into the U.S.
If the U.S. government starts shooting people crossing between ports of entry or using drones and hellfire missiles on them, it is unlikely to actually hit anyone with drugs. We will, however, probably kill a foreign national committing a misdemeanor. Again, this is likely to unite most of Central and South America against the U.S., along with creating the rest of the problems described above.