At some point, Mexico ought to be considered a failed state…
Agreed. Cartels run the country. The government is mostly corrupt and completely ineffective.
Edit: admittedly, a rather loaded statement. There's a lot more complexity involved, but essentially, it's an analogous situation: corporations and cartels are dictating politics. This is corruption! (Perhaps it's too much to call it a "failed democracy", but it's certainly a "subverted democracy".)
In the context of illegal drugs, Mexico would not be in this state without the US; and vice versa. Is it a parasitic or a symbiotic relationship...?