I have heard that in Spain there are distinct dialects that separate the Spanish spoken there. For instance, in Catalonia, apparently the "s" sound becomes "th."
I was wondering if similar differences exist in France and if so, how many?
As far as Spanish is concerned, it seems you are referring to the way the letters 'c' and 'z' are pronounced compared to the 's' letter depending on the region. Catalan people speaking Spanish are following the standard usage to pronounce the formers like the Engligh 'th'. In some Spanish regions like parts of Andalucia, 's' is pronounced like the standard 'c', that is the "ceceo". In other areas like the Canarias Islands and Hispanic America, there is no distinction between 'c', 's' and 'z' which are all pronounced 's', that is the "seseo".
There are certainly similar patterns with French, like the distinction between "in" and "un" being lost in Parisian French but still strong in parts of Belgium, Southern France and other areas. The missing "ui" in Belgium, which is pronounced "oui", and so on.
It is unclear if you refer to Spanish spoken in Catalonia or Catalan. The latter is not a Spanish dialect but a language of its own. It happens to be also present in France, along other languages like Basque, Britton, Corsican, Occitan, Flemish, Alsacian, not to mention Creoles and other languages from overseas locations. There are also (Old) French / "Langue d'oïl" dialects, like Picard (a.k.a Chti), Gallo, etc. and modern French variants like the ones spoken in Quebec, Belgium, Switzerland and Africa.
Whether with close root with modern French or not, regional languages usage widely varies and has a tendency to fade out especially with younger people. Nevertheless, they generally leave distinct accents often easy to spot.