I agree that La Eme does not have the manpower to go to war with the AFO. They do, however, have significant influence on the street. Most Surenos have to pay taxes to La Eme. When a Sureno goes to jail, he is indoctrinated. When he gets released he has to toe the line or his return to jail will be highly unpleasant.
Have a look at this post, and the whole blog for that matter, for interesting info:
