The last time I went through MIA, it took about 2h. And I'm an American. With Global Entry. This is just anecdotal, of course, but I consider MIA to be the worst airport in the country for arrivals.
Just waiting for your luggage PRIOR to clearing customs can take over an hour. I've barely made 2½ hour Int'l-Domestic connections at MIA, because of the time to reclaim luggage and clear customs. Not to mention that MIA is huge and an absolute bear to navigate, especially if you don't know the airport.