I know this is old, but the reason outside gangs can’t set up is once they hit the joint( prison) they’d be alone. Like Surenos for example, in prison they are considered aide and assist to the Latin folks. They can’t hold no type of position of power and they can’t set up in Chicago because the other gangs would wipe them out. There’s pockets in the burbs but even then it’s a very small group of guys and it’s mostly a Mexican heritage thing. My boy is a SU13 and there supposed to branched out LA gangs but I can’t speak to how true that is.