Originally Posted by
Cometintintin
the answer is "you do not need your passport for the Mia-JFK flight"
The downsize is that you will have to tell the agent in MIA to check you "only" for the MIA-JFK segment. She/He wont need to see your passport. In JFK you will have to get your bag, (your passport) and check for the international segment.
A little bird has told me:
This is bad advice and the OP will find themselves standing at the counter in MIA while the plane takes off to JFK if they show up without a passport.