I am considering applying for a Masters degree in Mathematics, and i
have narrowed my choices to Universities in France and the USA.

So, i'd like to know how are the graduate mathematical departements
of French Universities and Grand Ecoles compared to those in the USA
(no limitations to particular institutions).

Please note that i am particularly interested in the field of Chaos
Theory, but if such a strict comparisson is not possible even a more
general one will suffice.

I to do a little bit of research on the French University side of your
question but found it much too difficult since I have not taken french
in 15 years.  But I do remember my french teacher telling me that the
universities in france were supposedly equal.  I am not too sure how
true that is though.

When searching for the US side of the question I found a side directly
related to the Field of Chaos.  http://www-chaos.umd.edu/ that will
give you an little more understanding of what is offered at the
University of Maryland.

I hope this information proves to be at least a little helpful.  Good
Luck with your search.