How much time should we allow ourselves in the Geneva airport to fly back to the states?
Check with your airline to see how early they want you to be there. I would think 2 hours ahead of time is enough, but US-bound aircraft may have lengthier security requirements.
Are you returning a rental car? If so, allow yourself even more time as the airport is on the border and depending on which country you rented your car from, you could end up returning it to the wrong side and wrong country which costs an extra drop off fee and extra tolls. It is not very well marked and we spent an extra 30 minutes trying to find the right drop off point.