Not much to add to the above, except to say that when I went through 10 days ago (lhr-mia-nas, BA to AA) the line to go through security after exiting CBP was so long that I turned around, went upstairs to the AA flagship check-in area (where TSA-Pre have an access) and went through the pre-check area there. With handluggage only (GA, and pre-check) I was plane to gate within about 35mins.
I’ve done that a couple of times in MIA, and something similar in Madrid too when coming back to the UK (just exit and go through fast track in departures, instead of transiting) from South America.