Mexican pot is greatly compressed in order to smuggle it in. This pot ends up flat and smashed by the time it gets to the user, and is also oftentimes very stale, as it takes a longer time to get to market, and while in transit is exposed to extremes in temperature and humidity.
This "flatness" cannot be undone. Once it is squished, it remains squished, and it is obvious by its' squishness that it has been compressed. Oh, and it is brown and smells of dirt and sweat.
By abusing the product in this manner, the active ingredient is degraded, thus lowering its' value. Mexican pot producers/smugglers are not concerned about this decrease because their business model values quantity over quality.
Domestic growers have a different business model. They value quality. The pot you get from them is a totally different animal: fluffy, green, and smelling of skunk. To compact and bruise their product would cause a decrease in quality and thus income. Also, compaction is not necessary because it is not smuggled long distances.
Also, unknown to you, their are two different kinds of pot: Cannabis Sativa and Cannabis Indica. The two look very dissimilar. Mexican is always Sativa, because that subspecies thrives in hot, arid environments. A farmer can "broadcast" seeds into his field and know that they will grow with a minimum of care. These plants will produce seeds because the male and female plants interact. Domestic pot tends to be Indica, which prefers a cooler, more temperate environment. Indica suffers in a very hot environment and cannot be grown in most of Mexico. Also, domestic growers strive to produce a seed-free product and will kill the male plants as soon as the display their sex, as the presence of seeds reduces the value of their product. As a result, domestic pot costs MANY TIMES what mexi pot costs.
Because of the factors cited above, it is very easy to tell the difference between the two types of pot by simple visual inspection, and why I consider your thesis ludicrous. (your thesis being "high quality Indica coming from Mexico, sold as medical pot, and thus benefitting drug lords")
To sum up, you may dispute me according to what you have read, but I will dispute YOU based on what I have seen and experienced with my own eyes over the span of 20 years of smoking all types of pot. You are entitled to your own opinions, but you are not entitled to your own facts, and I hope this helps cure you of some of your ignorance.