Domestics always have to be recleared at MIA and rechecked in the dedicated area as you sweep around the baggage hall. One ticket or two tickets makes no difference. Some international connections can be ITI and avoid it, if on one ticket.

MIA actually does the main custom clearance upstairs in the CBP passport check process. They also have screens linked to baggage, and while spot checks are done in the baggage hall, including the use of canines, they actually could move to the European model with only a small amount of extra technology - while your passport is being checked the CBP agent could get a CT scan of your baggage and ask detailed questions about the contents. MIA also has a dedicated pathway back to security and then airside, a bit like PHL, but it is more than technically landisde.