Well, I thought the point was that Europe was very poor due to their resource wars and that they wouldn't be able to afford to contract RobCo, Poseidon, Vault-Tec or West-Tek and that they wouldn't be able to afford to produce Power Armor or Energy Weapons or other such items cause lack of money, resources, time and power struggle.
Which would mean that a game set in France would not have a lot of connection with the Americana games.
Why are you so fixed on setting it in France?
I always picture Germany or Great Britain (or Sweden... nah, kidding) And of course it would be a different Fallout experience since the continents differed a lot from each other in terms of resources, economy, allies and enemies pre-war. But there would be energy weapons, Germany designed two atleast, and Austria one.
I think Germany because of East and West Germany (How did that turn out anyways, with the time split? Since USSR still existed in 2077, did DDR and the Berlin Wall still exist? Did West Germany get American support? Things like that.) and as we all know, germans are good at everything involved with the word "factory" and inventing weapons. So we would have energy weapons. Maybe there'd be a nuclear power plant still standing and running and supplying some energy to some isolated and fenced-in settlements. I'd imagine that the wasteland would be a harder, less frendlier place than in USA. I would also like to know how the post-war East and West Germany turned out, like the west half of the game world is different to the east half of the game world. Maybe the Berlin Wall would still be there, and communism on the east side while it's more like USA on the west side. But still dangerous, because people are living in distress even more so than in USA. People would join groups that are not all too friendly because they will do things to get water and food, and factions like the Followers of the Apocalypse would love to help but wouldn't last, they'd be raided.
And I think Great Britain because it's easier to give a good reason for why they speak english (with a british accent aswell, maybe even some more scottish and irish) and they may had nuclear weapons (sure they are not allied to USA in the Fallout world, but they could still have them, aswell as things running on nuclear). Oh, and cars on the roads would be on the wrong sides aswell (sorry, left traffic joke)