Lol what FR cartoons are we talking about here? I hope it's something good like dubbed CN shows
It may be due to their accents. And they often use expressions that are hard to translate JIT. I know it was hard for me to understand EN cartoons. Plus hey are often dubbed in Belgium, so it's harder to understand because they may use terms and sentences from there
Unless you mean QC dubs like the Simpsons or Fox/Adult Swim's shows