MIA cane be a real mixed bag especially the AA Terminal where while they have a dedicated Global Entry Customs exit line, the CBP Employee still question you and that can take a bit especially if he/she decides that the person they are speaking with is a potential bad Apple.

Three times I have unfortunately been labeled a bad Apple and then after an X-ray or the last time a physical hand search of my luggage I am determined to be a good Apple and free to go, still probably faster than without Global Entry but longer than other airports.

The odd part is that at DFW/IAH/JFK/EWR/LAX/MCO I am never questioned nor searched, just MIA.