To start off with, I'm not sure who would really consider Mt. Hope to be "nearby" to Charlotte. It's over a three-hour drive.
So, I'm not quite sure who deserves the blame for the BSA FUBAR:
-It sounds like the BSA were trying to save money on buses, but there may have been a practical issue here (sheer bus availability becomes a thing at some point), particularly at peak times. Ditto logistics with loading areas at the Jamboree location. The lengthy at-airport waits seem to be a problem, however.
-The BSA probably also deserves a bad note for running everything out of CLT. CVG, RIC, and a few other airports aren't substantially further (and a few are closer). If staffing was an issue, it might have behooved American to proactively cooperate to book some blocks of fares out of other airports in the region (ROA leaps to mind, as does TRI). I suppose this was a coordination thing, but it feels to me as though taking some effort to distribute the boarding load should have occurred to someone in that chain.
-As to the staffing situation at CLT...I'm guessing that AA saw a higher-than-normal pax count but didn't take into account the mountains of checked luggage going out (or an unusually high number of kids flying, for that matter). Presuming that positioning a bunch of staff at CLT for the day would've been problematic, though, I have to wonder (if there was any advance knowledge at hand) why the airport wasn't involved here. I'm thinking of the flexible status of many agents at, for example, YUL (as an outstation for several carriers). Again, distributing the departure load to a few airports would have gone a long way here.
-As to marshalling the waiting scouts? Who knows who is to blame for that. Could be AA. Could be CLT. Could be the BSA. Could be a mix of all three and a "disaster cascade" (e.g. CLT orders the buses to be moved and fouls everyone else's plans and hell breaks loose).
So a lot of the blame does land on AA and some on the BSA, but in some respects if everyone was trying to keep the operation "simple" in terms of logistics (one departure point, one arrival point) it was probably going to be a fragile situation no matter how much planning went into it unless AA was ready to completely rework their operations for the day at CLT. BTW, presuming it was 10k scouts traveling out of Charlotte, that's over a 10% bump in "average day" traffic (and in terms of initial boardings, given CLT's hub nature, I'm guessing the impact was easily 2-3x that percentage-wise, possibly even more, all of whom probably had more verification going on than normal as well as bag-checking).
Honestly, given the numbers involved and the like it seems like it is entirely possible that this was a situation that was simply unfixable in terms of counter space and so on. There's such a thing as only being able to push so much water through the straw.
Over on the DFW flight: My immediate thought was "If DFW couldn't take them, would SAT have been capable?" Of course, I suspect that (as AUS does have CBP facilities) if the crew had died they probably would either have been disembarked or been facing some ugly consequences if the delays went past a certain point (since sooner or later, health issues and the like are going to start coming into play).