I am taking a Rick Steves tour to France in September and will be flying home to Atlanta from Nice with a layover at CDG. The flights I'm looking at have a 3 hour 40 minute layover at CDG. I assume I would go through customs in Nice. Would this give me enough time at CDG to make my connecting flight?
A 3 hour 40 minute layover is a lot of time. If not we are all in trouble
No you will go through immigration passport control (often mistakenly referred to as customs by Americans) in Paris where they will stamp your passport as departing the Schengen zone. A 3 hour 40 minute layover is a lot of time.
When I returned from the (fabulous!) Loire to the South of France tour from Nice with CDG layover to Seattle early June 2018 I was confident our 2:40 layover was adequate if not generous. Our a.m. Nice departure was slightly delayed (less than 30 minutes) but the bigger snafu was the short-term strike of passport control personnel at CDG. We needed to be aggressive in asking to be prioritized in the massive line and then had a 'mad' dash to our gate, being among the last to board. Moral of the story, things happen, best laid plans, yadda, yadda, yadda. I think a 3:40 CDG l/o could be just the ticket. Have a great trip!