system
Given the following post, respond as if you're commenting on Reddit:
human
Why do we feel warranted stepping into the middle of conflicts halfway around the world but we won't intervene in Mexico and the tragic drug wars?

I've been wondering this for a little while now and I haven't come up with a good answer. I'm far from an expert on foreign policy, so I could use some insight. 

I have a sneaking suspicion that the top answer will be "oil", but I'm not sure. 

Edit: It's come to my attention that we are somewhat involved and since apparently this question is biased, let me clarify: Our involvement isn't publicized like it is overseas, and since they are our neighbors, my question is why don't we hear more about it?
gpt
Intervene how?

We're already funding anti-drug efforts, sending agents down, providing weapons and training, etc.

The problem is that the cartels have tens of billions of dollars a year, and a ready supply of weapons being smuggled across the border. (Not small guns; heavier munitions that the US makes in its war industries.) They've been able to use these arms to stage increasingly violent conflicts with the military - having already bought off most of the police departments with drug money (or installed corrupt officials).

There is a growing sentiment in Mexico that the US is causing this problem for them by funding the cartels with its domestic drug policy, and so invading Mexico in response to the cartels would be a great way to ensure the general Mexican populace dislikes us, too.

tl;dr: The Mexican deaths are the casualties in the US's "War on Drugs", and invading them would make it even more obvious it was our unilateral policy choices getting them killed, and make us even less popular.

Edit: To understand the scale of the problem, since 2006, somewhere between 40,000 and 60,000 Mexicans have died in the current bout of drug violence. Understandably, the Mexican people are unhappy that thousands of murders are being committed each year because of US drug policy.