Flight transfer in Rome (FCO) Airport

If the airline is saying the connection works, then you need to trust them, but be prepared. You do not mention the airline, but it is worth looking at options, and if there is something better, then request a change. That should occur at no cost, probably best to talk to a representative rather than book on your own.

When you land in Rome, you will need to go through Schengen exit immigration, that is usually quick, but no added security that I am aware of. FCO does not participate in any US Immigration activity, but it is not unusual to have additional document checks and random screening at the gate. Exactly how much time would be dependent on what terminal and gate you fly into, and where your departing gate is.

I would agree with Paul. Should be enough time but it is close. I would check to see if there was a later flight.

That is very tight, but as others mentioned, if the airline has booked you on this itinerary, they are responsible for getting you where you need to go. (I'm assuming it is American from Rome to PHL.) As someone who lived in Rome and has used the airport many times, I've learned that things are not close. The international terminal is quite large and even if I were transferring from one international flight to another, I would consider that too close for comfort. (Think about it: it takes a while to get off the plane itself, leaving an even shorter window of time.) The Rome airport does not have US Customs and Immigration screening (if you're talking about the type where there is a US customs official stationed there). If it were me, I would tell the airline that I wanted to change my itinerary.

David in Seattle's suggestions above are wise.