Customs

Do you have Global Entry and/or Precheck?

Two hours is cutting it close. You will have to go through customs etc., get luggage, possibly travel to a different terminal via the Airtrain, and then go back through security and get to your new gate. You should probably allow 3 hours at minimum.

Thanks
One of has a Nexus card...Does that work as GE

Have you looked at the on-time performance record of your CTA-JFK flight?

Do you know which terminal(s) your arrival and departure flights use at JFK?

2 hrs MAY be enough IF everything works, at or near peak efficiency, and you are seated near the front of the plane.

With a separate booking, if you miss the onward flight, its your dime to get the replacement. The walk up fare is likely to be spendy. Another risk is, will there be a flight with open seats to be had? Do your research and make an informed decision. Personally, I would give myself more time.

Nexus card-- http://usa.immigrationvisaforms.com/travel/nexus-pass

-"""NEXUS Pass is a border crossing card for expedited US Canada Border Crossing. NEXUS cards provide expedited travel at the US Canada Border for predetermined low-risk Canadian and US citizens."""

NEXUS does not look to be of any help for your situation, even if everyone had one

I have seen very long, time consuming lines at JFK's for passport control/ immigration . Luckily I could skip past them with Global Entry. Then you still have to go through Customs. I have been challenged at JFK and sent to Agricultural Inspection for allowed items. Two hours seems seems to be high risk for making another flight unless you have Global Entry.

Thank you all. Great help

Check historic data and hope for the best: https://awt.cbp.gov/

CBP closely monitors the flight processing times, commonly referred to
as wait times, for arriving flights at the busiest international
airports. The data provided in this report will show the number of
passengers processed on flights arriving in each hour based on how
long it took for those passengers to clear Passport Control.

Flight arrival patterns can vary considerably by time of year and day
of week, as well as by time of day. To help travelers in planning
their next flight, CBP is providing the public with historical data
for the wait times at the busiest international airports that can be
used to estimate possible wait times by airport and arrival terminal.

As you are planning your next flight, remember that CBP airport wait
times do not include time to retrieve baggage or navigate through the
airport. These times should be factored in as well if you will be
scheduling a connecting flight. Always consult with the airline and
airport authority for additional guidance.

We had a 1:40 connection there earlier this year and even without GE and getting sent to secondary agricultural inspection (had been hiking in sheep pastures) followed by a terminal change, we made it to the next gate with time to buy snacks before they called for our next flight.

It's not ideal, but it's reasonably possible, IMO.

You didn't mention when you will be traveling. Summer is a very busy time for int'l travel, and it seems to be getting worse every year. I was shocked at how long the lines were at SFO this past May. I think it took us 2 hours to clear both passport control and customs. I doubt that JFK is less busy. The fact that someone else made a connection with a 2 hour layover wouldn't reassure me. I'd aim for at least 3 hours.

2 hours is a little risky even assuming that your plane is not delayed. If your connecting flight is on one ticket (with your flight from Italy) then they have to put you on another plane. But if not you are out of luck. For that case buy either refundable ticket or good travel insurance.

One of has a Nexus card...Does that work as GE

The Homeland Security web site says that NEXUS includes all the benefits of Global Entry. However, that won't help if not everyone has it.

Yes, Nexus will work as Global Entry -- but only for the person who has it. The benefits are not sharable.