Thank you for your post. In order to create a scale bar, you need to use a non-Geodetic coordinate system. When you try to create a scale bar there should be an error message that states “Scale bars cannot be created with a geodetic (i.e. lat-long) coordinate system. Perform a coordinate system transformation to a projected coordinate system if you would like to create a scale bar.”
Therefore, if you would like to create a scale bar, you need to perform a transformation on the MAP View that includes the French boundary. To do this, you open the MAP View editor > Perform coordinate system transformation > select a different coordinate system. I would recommend that you transform it to WGS 84 / Pseudo-Mercator (EPSG: 3857) since your data is already in WGS 84, however, you can transform it to the coordinate system you would like to something that would better fit your project needs.
Lastly, there is a feature request to have the ability to generate geodetic scale bars, I’ve gone ahead and added you to this feature request as well so you will be notified if and when it is implemented.
If you have any questions or issues please let me know.