You cannot have missed that I made those points before you reminded me of them.
The real question is whether this activity is an official act of war by Mexico; or the result of corruption, and thus non-official.
I seriously doubt that this is Mexico's official policy.
Actually, the point is even more subtle than you suggest.
Fact: The Mexican army is corrupt to the core.
Fact: The Mexican government knows that the Mexican army is corrupt to the core and does nothing to stop said corruption.
Result: The actions of the Mexican military reflect the actual policy (albeit not the stated policy) of the Mexican government.
If the first two statements above are true, then the Mexican government is complicit and it is an act of war.