Here I am! Yes, I am vegan and have traveled in Italy and France among other countries.
In general it is easier to get vegan food in Italy over France but doable both places.
In France, it is sometimes difficult to make yourself understood (even with translation cards) that butter is not vegan. Often veggies will come cooked in butter and it is not evident from the menu. Salads are easy and I can usually find a sandwich from the shops that sell to-go sandwiches that are vegan. Paris has terrific ethnic food and if you like falafel you will be in heaven. Idaho is sort of a falafel waste-land so I try to eat it every day when I am in Paris. You do need to be careful with soups as they will sometimes have cream or creme fraiche added.
In Italy, it helped to have a couple of fall-back dishes to order. Fresh pasta often is made with egg so is not vegan but if you aren't fussy about a little bit of egg you'll be fine. I usually would get Pasta all'arribiata which is a spicier sauce, or some kind of pasta with garlic and olive oil and order a side of veggies to put on it. In variably the side veggies were eggplant and zucchini so I was mightily sick of them when I finished my time in Italy. Pizza is easy to order senza formaggio - no cheese. The wait staff will sometimes repeat back with raised eyebrows, but it has always come out the way I wanted it to. Salads are of course easy and soups are often vegan.
I do recommend carrying translation cards with you. I use ones from this website. I have them clipped to my phrase books. Occasionally when I could not make myself understood to the waiter I've showed the card and a couple of times they have taken it back to the kitchen, then come back and pointed to things on the menu that would work. I always leave a nice tip...even though tipping is not customary...as a thank you for the extra work.
You've posted under the Rick Steves' tour forum, not that it matters. However, I've done 7 RS tours and have rarely had problems with group meals. In almost every circumstance the chef was able to accommodate a vegan meal, both in Italy and France.
Let me know if you have specific questions.