Wall Street motivates them to extract revenue from wherever, even if it harms United States security. Tariffs, when surgically applied, directly reverse what Wall Street wants, and directly affect business executives' decisions. I've seen it happen. Right now there are 25% tariffs on some Chinese goods, and it directly changes global market behavior.
Regarding Mexico: It is a failed state. We could easily declare war on the cartels, and drone strike them into eternity. Then Mexico can regain power (or we can annex them if they want...but only after we deal with the cartels like the terrorist they are, not as "US criminals who have constitutional rights").
Agree on China. I work with good people there, but the regime is not a positive contributor to the well being of the world.