I think the shows in general don't want to have to constantly explain, "Why didn't they just call so-and-so to help out." I'm okay with them keeping to themselves for the most part unless a crossover or guest shot is really warranted. Maybe BL didn't want to invite other heroes to possibly run afoul of the US government, maybe he just likes to take care of his city himself, etc... all the shows would get repetitive if they have to explain it all the time, imo.

And Gambi seemed to have a non-reaction from what I recall. Jeff unloaded a lot of info in that scene and I think eveyone was just taking it all in. (his reaction could have been surprise that Jefferson ever thought of Superman as a comic book - it seemed vague enough)