Do cartels even exist in the US? Why would cartels be in the US with open borders?
Doesn't open borders mean US law enforcement, like the DEA/FBI, gets to operate in Mexico now? How would the cartels survive under that, if they can't even survive in the US?
Yes, they do. Quick googling (reputable sources) show that. They're especially prevalent in the prison system. Production and transport is through Mexico but consumers are in the US so they exist on both sides of the border.
Why would the cartels not move into the US given the chance? You underestimate their reach, there's no way the DEA/FBI could shut them down when they can't control the drug war as it is.
If you aren't aware of them in the US it's because they aren't as open about violence.
These cartels sound like super agile organizations that can execute any possible business plan, in any industry, legal or illegal.
In reality, of course, no such super-organizations exist. If and when the industry they have a comparative advantage in disappear, so will the organizations.
reply