I am flying from Lisbon to SFO on Delta and the connecting flight goes thru CDG airport in Paris. The time between connecting flights is about one hour. Is this enough time to make the connection? Where is the customs check - Lisbon or CDG?
They'll stamp your passport in Paris, but you don't have to collect any checked baggage there. That will happen when you arrive in San Francisco. One hour can be enough time, unless of course there are delays.
Your customs check is at SFO. When I flew LIS > CDG > MIA, I did not go through any passport or security points in Paris since I remained airside for the transfer. In my case, one hour was fine. Check with your airline to confirm that yours would be similar flight change.