Not sure.
Weather can play a major factor both in EWR and MIA. If your flight is delayed even a little then you would be squeezing it. If your flight arrives on time it's somewhat possible.
However, after looking at the terminal map the one main question is how many people are you travelling or are you alone? And if there are others, are there any kids?
The reason I ask this is because the AA terminal is huge and depending on where you will land in the terminal can take quite some time before you can even get out of it. Then you would have to collect your luggage and then make your way to the terminal servicing Alitalia which is across the airport. Luckily, for those in the know, there is a moving walkway system that goes between terminals which can speed this up and it's located on the third floor, accessible by elevator.
IMO if you are travelling alone, I would say that if it were me I would risk it. However, if you are travelling with a bigger party then I wouldn't. Luggage can take a while to collect especially if there is more than one checked bag.
There are pros and cons to look at when making this decision. You also have to keep in mind that while there are horror stories with Alitalia and luggage, this does not happen to everyone, it is just that it happens with Alitalia passengers more often compared to other airlines. And, if you booked your travel with a CC that covers delayed luggage then don't worry at all, just book your luggage straight through.
P.S. Either way you decide, make sure that you take the moving walkway from the American terminal to the terminal that services Alitalia. There is not a lot of info in the airport that will direct you to it. It is located on the third floor. If you can't find it ask airport staff. Otherwise if you just follow airport signs they will tell you to walk and it is a very long walk from American (Terminal D) to Alitalia (Terminal H)
