But France is Western Europe, not central. Is it the prevalent brand there too?

>Usually the countries considered to be Central European are Austria, Croatia, the Czech Republic, Germany, Hungary, Poland, Slovakia, Slovenia, Switzerland; in the broader sense Romania and Serbia too, occasionally also Belgium, the Netherlands, and Luxembourg.

I think that Martini was overwhelmingly the most prevalent brand of vermouth the world over. That's certainly the case in the US.

Vermouth is from Italy, which is more Central European than Belgium, the Netherlands, or Luxembourg.

I've never heard people refer to Italy as "central Europe", personally.