Culture in Schaumburg, IL doesn't reflect the start-up environment that you can feel in Paris. Other colleagues are very judgmental, no "friendly" environment.
No casual clothes (No jean or sneakers except on friday for example).
If you live in Chicago, forget it, too far away even with a car (awful traffic).
No budget for old projects even if they are used by the majority of the clients, too much into the future project sometimes.
Found them very picky about expenses out of work (no cars of hotels for more than a week if you're hired from the french office to the US for example).