Actually Mexico doesn't control the tap. The US does. Illegal immigrants and the US drug epidemic are symptoms of failed US policies and our oligopoly.

If companies paid higher wages and were punished for hiring illegal immigrants, more Americans would work the jobs that illegal immigrants now work, and Americans would take fewer drugs.

Simultaneously, if we stopped sanctioning 1/3 of the world (including a LOT of Latin America) there would be fewer refugees streaming north to the US.

I'm not naive enough to believe either of these changes will happen any time soon. The oligarchs have firm control of the US government.

Trump and every other president will continue to rant about the symptoms, but none of them is brave enough to address the root causes.