Technically, the luggage is "checked through" (i.e., tagged to its final destination) even on an international-to-domestic connection. But it must be claimed and submitted for Customs inspection at MIA, and then dropped at the re-check desk just past the Customs hall -- no re-tagging required. On an ITI connection from AA/BA to AA at DFW or MIA, the bags can receive a special ITI tag, which would obviate the need to claim and re-check the bag at the airport of entry.

In either case, the passenger will find himself landside after exiting the Immigration/Customs facility, and would have to clear TSA security to get back airside.