Alsatian is probably one of the local languages which suffered least due to Alsace having been conquered by Germany in 1870, and being reintegrated with its own set of laws and exemptions in 1918.
Hell, the republic just grouped everything which wasn't standard french under patois, regardless of them being languages, dialects, creoles, ….
Though just so we're clear, this is a long-standing issue of the french state and its centralised habits: Louis XIV banned Catalan back in 1700.
They did though, Louis XIV banned Catalan in 1700.
Although I guess it was not really about the "common people" and more about legal and official acts being in Catalan in Roussillon/Northern Catalonia[0].
I think of my Alsatian colleagues that learnt their regional language mostly from their grandparents. That skill is still very useful on the other side of the border but you wouldn't know it if you ask the ministry of education in Paris: the dialect of the Haut-Rhin is relatively close to Baseldüütsch and for those that didn't learn at home, bilingual school opened the doors of employment to a lot of people there. There is a net regression of Alsatians who are functional in German, either dialect or standard. Good job opportunities in Basel are being increasingly filled by Germans as the generations progress, while the economy stagnates in France. Back at home, the regional reorganization of France under Hollande is unlikely to help efforts to preserve the regional language since Alsace has been incorporated into a mostly francophone eastern megaregion that has little interest to spend money on the promotion of some 'backwards' regional language or even the foresight to encourage a second language that is not English.
Anyway, the discouragement of regional languages is not only a problem in France, as others have noted. Next door in Switzerland, the regional patois like arpitan (a variety of franco-provençal, perhaps related to Occitan) were discouraged for a long time. Completely different to the approach adopted in Alemanic Switzerland.
My personal opinion: the desire to 'live together' starts on the local, not national level so more efforts are needed in that direction for a functional society and regional languages help.
Normands spoke French long before some emigrated to North America. Just ask the English.
In addition, when the colonists settled in New France and mixed together, standard French (the concept probably wasn't there at the time, but administrative French maybe) was the natural common denominator for them.
[1] https://en.wikipedia.org/wiki/Ordinance_of_Villers-Cotter%C3... [2] https://en.wikipedia.org/wiki/Language_policy_in_France#Fren...