Not really familiar with Miami but would have thought that two hours would be a satisfactory minimum. It's only a tiny possible percentage point but I always try to sit as far forward in the aircraft on a US inbound and I go like smoke between the gate and immigration. The other people on the same flight are just another blob to clog the gates before me if I don't get there ahead of them. Three hundred Hondurans, although it's unlikely the flight consists entirely of Hispanics, could take a little longer for US immigration to process than, for instance, the same number of Poms.