Train travel Salerno though Tuscany to a major city for flight to Paris

What do you mean by a "major Roman city"?

Victoria, you may get more answers if you post your question in the correct area. You have posted it in the section designated for reports on trips forum users have taken. Try posting in transportation or general europe areas.

Just an FYI; Lucca, Florence and Pisa are all in Tuscany.

Have you looked at the Trenitalia website to look at how long your "scenic" (FWIW, I don't think many of the Italian train routes are particularly scenic) train ride would take? Since you don't want to stay in Florence, I picked Siena as a decent size place that you haven't visited yet. Best I could find with just a quick search was a few daily trains with a couple of changes that would take almost 6 hours. That's going to pretty much blow the whole day right there. You could stay there 2 nights, and get a day tour on the second day to see some of the hilltop villages or do a wine tour.

I'm assuming you meant a major ITALIAN city, from which to fly to Paris. That would be Florence. If staying in Siena the night before your flight, you'd want to book an afternoon flight. I'm also assuming you would be flying into Paris the day before your flight back to the States. It probably would have made more sense to book an open jaw jaw ticket so you could have flown home from an Italian airport ( unless you are spending several days in Paris before going home).

You could train to Venice and fly to Paris from there.

You are planning to be in Paris the night before your flight back to US, correct ?

There are normally no one-way car rental fees for pick up and drop off within Italy.

Pisa airport is another Tuscan option for flights to Paris, for instance on EasyJet to Paris Orly airport. (Don't take RyanAir to Beauvais airport because it's the furthest away from Paris.) See also www.skyscanner.com.