Sometimes I feel we're overestimating the power of the cartels in the USA a bit.

In Mexico for instance the cartels largely have the power to do as they please, but in the USA I really doubt they're just going to get their way by kidnapping or murdering feds and their families. If they really had that power, we would've known by now.

When DEA agent Kiki Camarena was killed by the Guadalajara Cartel in Mexico (not even in the USA) it meant the end of that cartel. The US put such an amount of pressure on Mexico that they had to crackdown on that cartel until they were no more. That was basically the only time an American LE agent got hit by a cartel and it concerned a DEA agent (forget about an FBI agent).

Mexican cartels aren't stupid and they're not going to target American LE leave alone feds. Their direct infiltrative power in the USA is limited and that's working just fine for them. They fight each other over in Mexico for the smuggling roots, but once the dope hits US soil, they leave it to street, prison and biker gangs to take care of all the rest, mid level wholesale and retail.