For the 1700's, you can forget it.
France was the most coherent dans the most solid kingdom of Europe.
You already had the worst possible internal conflict with the civil war following the revolution, and it did not break up the country. It was a conflict about legitimacy's principles, about social and political values, about property, it was even religious. And however, the national unity was never in question.
But to have your scenario work, you would have to resort to some kind of massive asteroïd factor.
If you bring it back things to the 1500's, then you could imagine more easily a break-up of the country on religious bases. Take the times of the war beteween the catholic league and Henri IV.