Each set is autonomous for the most part. The crips in LA use to be more hierarchal. In fact they became such a force that a bunch of other gangs came together and formed the bloods. So basically bloods and crips is just a matter of alliances. When the bloods and crips starting spreading out out across the country, the actual affiliation became less meaningful (not that it doesn't stop them from killing people because of the color of their clothes).