SFO/LAX (whichever airport you use) > VCE (via any European hub) >visit Venice and Treviso > Lake Como or Lake Garda > Florence/Tuscany > Cinque Terre > Rome > Fly back from Rome FCO.
Since you are interested in the wine regions, then I would stick to Lake Garda, rather than Lake Como. They are equally beautiful, but Valpolicella is really close to Lake Garda, and if you are interested in the prestigious Franciacorta bubbly wine from the homonymous region (between Lake Garda and Lake Iseo) you can visit that too. 
In that case I would also rent a car, because it will be convenient to visit rural wine areas both in Veneto and in Tuscany. 
This is my revised suggested itinerary.
-SFO/LAX (whichever airport you use) > VCE (via any European hub) 
-Visit Venice and Treviso, and possibly Verona (none of these cities need a car to visit). 
Venice deserves 2 or 3 nights, and maybe an extra one for a day trip to Treviso.
Verona deserves a full day, so you could go there from Venice in the morning and spend one full day, and sleep one night in Verona.
-The next morning rent a car in Verona to see the lakes and the wine areas.
-Visit Lake Garda, Valpolicella, Franciacorta (lake Iseo) with the rental car. You will need at least 3 nights for the lakes.
-Drive with the same rental car to Tuscany's wine area of your interest (Chianti hills, or also Val d'Orcia for Brunello di Montalcino, if you are interested in wine areas). Stay in that area with the car.
-Drive to Florence. Return the car upon arrival.
-Visit Florence for 2 or 3 nights.
-Train to Cinque Terre
-Visit Cinque Terre for 1 to 3 nights.
-Train to Rome
-Visit Rome for 3 or 4 nights
-Fly back to US from Rome (FCO). If you want there are non stop flights from FCO to SFO (ITA Airways and, in summer, United) and to LAX (ITA Airways)