If it's all on one ticket, you'll simply be put on the next AA flight to Orlando. Whilst 90 mins is a legal connection, there's pretty much no chance you'll make it with immigration procedures. I don't understand why you would drive to Ft Myers? Is that your final destination? If it is, there was no point in booking the Orlando flight in the first place as Ft Myers is much closer to Miami than Orlando? If you don't take your flight to Orlando, the rest of the itinerary will be cancelled as you have to fly flights in sequence. Depending on your final destination, I would consider calling AA to cancel the MCO legs.