I think snooker helps in the following ways:
1. Improves alignment
2. More care in taking stance and maintaining body position during the shot.
3. Trains the eyes to focus more tightly on the pot angle required.
4. Necessitates and develops a straight cue action.
A couple of things to watch out for:
1. Cut angles are slightly different due to the smaller balls. Hence, you may cut the balls a little thicker when returning to US pool balls.
2. Positional play is affected due to the lower ball weight in snooker.
3. If you're playing on 12' directional nap cloth, the effect of some pots, and some shots played with english will vary.
With that in mind, I think many pool players would benefit from some occassional drills on the snooker table. Especially longer potting at relatively full angles.
Colin