If you are flying from the US and have not flown to Europe before, be aware that most flights leave in the afternoon or evening and arrive in Europe on the next day, so you essentially lose 1.5-2 days to travel getting there. Coming back to the US it's usually one pretty long day, especially if you are headed to the West Coast. Next thing to plan for is that each time you change locations it will probably take 1/2 a day to check out of your hotel get to the airport or train station, actually travel, then get to your hotel at your destination. Currently you are thinking 7 destinations for 14 days. Three of those days will be used in travel to/from Europe so that leaves 11 days for actual time on the ground, which is why most will recommend you pare down your plan. Also consider your plan by nights, knowing 2 nights in one place just gives you 1 full day.
Here is what I would do if you want to see Paris:
Day 1: Fly to Paris
Day 2: Arrive in Paris
3/4: Stay in Paris
5: Fly EasyJet or another airline to Venice
6/7: Venice
8: Take a train to Florence
9/10: Florence
11: Take a train to Rome
12/13: Rome
14: Depart Rome
If other cities have a priority then you will need to drop something else.
If you have a little more than 14 days you could also consider Rick's 14 day Best of Europe tour which gives you a smaller taste of more places. It's easier for a tour to move faster and cover more territory than for you to do it on your own. I would still want to arrive in Paris a couple of days ahead and add time in Rome at the end.
https://www.ricksteves.com/tours/europe/europe-14-days
Or you could consider Heart of Italy which covers 3 of your destinations in Italy in 11 days (plus a couple you haven't listed) and perhaps you could add some time in Paris at the end.
https://www.ricksteves.com/tours/italy/heart-italy
Have fun planning!