Well, i'm french, so i can shed some light : will it work : in short, no, this kind of message will have little impact, but at some point, if you have those messages among other of the same kind, people may consider not taking the car when they can do otherwise.
Basically, regarding how the country is organized, i'd say people already only take the car when they have no choice, there are still a couple of situations where a bike could do (like the daily trip to bakery at 2 km), but i would say that people already try to spare the car trip when they can (also consider that gas/fuel is 50% more expensive than in the US, due to heavy tax system, and this is the most impacting message they can do).
One better solution would be to have a better pro-active policy toward bringing the services and goods at a bike/walk distance, the cities use to have the infra structure, it's just been abandoned for activity zones with big supermarkets/shop, but it is still not too late to move backward (and some are already on their way). There is a big trend toward consuming "locally" (largely fueled last year by the covid context and lock-down), and this, imo, will help more than these messages, whose biggest interest is to please the ecology activists...