Going to jump in on this thread for some friends who are doing LHR - MIA - LIM on 26 Dec. They are travelling J but are novices.

They are flying
BA207 LHR MIA arr 1445 (a380!)
AA917 MIA LIM dep 1735

Assuming they arrive on time which is a stretch as it's the A380, they have 2h50 between scheduled arrival and departure.

What's the pattern they need to follow at MIA? From a comment up thread their bags should be checked through so just queue up for immigration (they have no global entry or precheck, just an ESTA). Typical wait times in afternoon? Then head for gate area D/E which seems to be where AA depart from? Best lounge for them to head for if they have time?

If they were to miss their connection can they self manage rebooking in the AA app if they know their AA PNR? Or just go to the lounge or somewhere else for rebooking assistance with AA? (It's a BA ticket but assume AA will just sort IRROPS on the day)

The next obvious flight to LIM would be 6 hours later AA1307 dep 2325 but this may be full in J. Are AA likely to offer anything other than their own flights, any other partners?

If they had to delay to the next day what's the process to exit MIA landside?

Thanks for anyone who can share their experience for the above.