Are you wondering which World War affected French arts more? World War II had a greater effect for many reasons.

Undoubtedly, World War II had a greater affect on French art than World War I did. After World War I, there were virtually no changes to the French Arts. They were in an era of prosperity, and they just kept moving right along. However, we will show you what was happening in French arts after both World War I and World War II, in order to prove the point.
World War I did not stop the powerful force of art that was circulating in France. During the time, different groups and individuals such as Francis Picabia and Marcel Duchamp, were springing up in other European countries in hopes of starting anti-Dada art movements. However, when the Dada movement came to France, they were fairly open to the anti-war ideas that Dadaism propagated.
Therefore, they were affected by the war in a sense that they were drawn to more peaceful forms of art. However, Dadaism actually started in Switzerland. Therefore, while there was an effect on French arts, it was at least slightly indirect.
We cannot say that art changed dynamically after World War II, but there was more of a change than after World War I. Before World War II started, many people were involved with experimental forms of art, such as surrealism. Many of those individuals just picked up where they left off, or never even left off anywhere if the war was not directly affecting their personal lives.
However, a few new areas of art sprang up that quite a few people were drawn to. No matter who wins a win or what the details are, an exchange of ideas tends to take place. Abstract expressionism and action painting from New York came into France.
Often after a period of war, people need to free themselves and engage in these looser types of arts. Abstract works do not have rigid rules, and people could free themselves mentally and physically. Going along with this idea is the fact that artists such as Jean Dubuffet and others like him came to the forefront of the artistic world during this period with cartoons, graffiti, and other cartoon-like images.
Perhaps one of the major changes though was the shift in artistic power from Paris to New York. Paris had always been at the heart of the artistic world, but after World War II, that influence and prestige moved to New York.
You might be wondering how we know that these are effects of World War II. Well, if you study history and other sorts of theory, you will see how people react in times of war and how people act right after a war. There is often a need for expression. Horrible atrocities were occurring in Nazi Germany right before these movements. Furthermore, the art world of France split immediately after the war ended. There was almost no lag time, proving that wars affect nearly every single area of life, if not all.