I have been trying to work out how a french Louisiana could grow to independence and power in a North America that still contained Canada, an iroqois-ish native state around the great lakes, the USA on the eastern seaboard and Mexico (though probably a bigger Mexico than OTL)
The main problem seems to be getting large numbers of people to settle there before 1720 or so. The farmland should be good enough once the people are in initially and the French AFAIK had a better record of keeping the natives onside so a large Metis-like population could also start to grow.
My best ideas at the moment are using the Hugenot emigration in the 1680s and the French famines in 1692-3 and 1709 to push lots of people out to the colony. Once there they can start to show that even somewhere that doesn't grow lots of sugar can be profitable. If those events can be used along with a mania for colonization or good old fashioned lying about how good it is then an initial population can be built that over time will grow to be a challenger to the USA after independence. In between there will be all sorts of politics with the natives, the british, the royalists vs seperatists, maybe even some supporting of Irish independence in 1798 if the catholic nobles end up out there...
