Concerning the issue whether it is time or not, I'm actually not sure myself. I've seen a lot of applicants (in the famous sticky application posts) having done 4 to 5 years of study before applying, so I wonder if I'm not a bit early indeed.
In France, the division of courses is rather fanciful. In three years you got the licence (=bachelor), the fourth is called magistère (or master I) and the fifth is the master II (and after that are the PhDs). A bunch of US universities (Stanford, Cornell) don't accept applications before the magistère (so, in the end, maybe midwestphysics is right).
Anyway, thanks for your developped answer, bfollinprm, and thanks also for the advices.
You mentioned that the "quality" of French universities is pretty bad. Is that a sentiment that is expressed everywhere? Has your experience been so bad that if you could do it again, would you go into a CPGE instead of a university? (I don't know where I'll end up for undergrad next year)
I'm not certain on the details, but the physics department at UJF (Grenoble) have an exchange agreement with BostonU. There was something about reasearch. Maybe you could look into that and see if students from elsewhere can participate.