Would language difficulties be considered a valid excuse for a poor masters performance when applying for a PhD?
The good news is that you have a clear positive trajectory, and I'm assuming your undergraduate scores are quite good to get you accepted to the French MS program to begin with. In this case you have a high undergraduate GPA, and poor 1st semester MS GPA, and a good 2nd semester MS GPA.
This is something you should put into your cover letter. Straightforwardly acknowledge your difficulties as succinctly as you can, but phrase your 2nd semester &quot;comeback&quot; as overcoming a difficulty through hard work and perseverance.
A script might be: &quot;I underestimated how difficult it would be to receive instruction in a language I didn't have a fluent grasp of, and my grades suffered in my first semester. However, through diligent effort to improve my French, as well as late nights studying my courses, I was able to gain good marks in my second semester. Therefore, while my GPA is not as high as I would like, I believe what I have learned in time management and self-study during the past year will help me overcome future difficulties that challenge any PhD student.&quot;
As to how potential admissions officers would react to such a statement is out of your control. If it were me and I was not in a top top program where I can afford to throw away 99% of the applications, I might keep you in the pile for further review.