From the example given, it can be said that a type of social influence called informational social influence is happening to the French people.
Informational social influence is a type of social influence where the individual conforms to a certain set of behaviors and norms because he or she believes that someone else is more knowledgeable about that situation.
In the case of Halloween, since it is an American holiday, the French are imitating traditions that the Americans do during the celebration since the French are unfamiliar with the customs that people do during Halloween.
