Imagine if the US were taking more and more territory from Mexico while illegally evicting and assaulting Mexicans to make room for US settlers. Let's say that they then made it impossible for Mexicans to leave or enter a narrow strip of land and denied them medical treatment and severely restricted food and water access. That and prior to the attack of the cartels, let's say 6 years ago, the US launched strikes against the Mexicans where a later report by the UN found that 80% of the dead were civilians.

Imagine then if that drug cartel itself was originally placed into power by the US to avoid the formation of rival organisations that the Mexicans could choose between.