Mexican Soldiers Freelancing for Drug Cartels on US Soil:
Gun-toting members of the Mexican military are crossing regularly into U.S. territory, where they are partnering with drug cartels and criminal gangs to protect sophisticated smuggling operations, according to Texas sheriffs and lawmakers.
It's pretty well known on the street that the majority of narcotics are coming in to the US via Mexico.
This is the unspoken reason why so many are hesitant to shut down the border. Shut off all those addictive drugs and our cities will burn, probably some of the suburbs too. Nobody wants to have to deal with this on their watch.