Short layover in Paris. Do I have to get my bag and recheck them before flying back to US

Depends mostly on whether the two flights are on one ticket or not. If it's a connecting flight ( even if they are different airlines) all on one ticket, then you should be able to have the bag checked all the way through to your US destination at the Bilbao check in.

By one ticket, I am assuming that means that I reserved them all at the same time and didn't do them separately. Then yes, all on one ticket, all with Delta.

If it is one ticket they will check your bag in Bilbao all the way to Atlanta and 1 hour 50 minute connection is good when traveling solo in good health

Even if it's not on the same ticket, you may be able to get it checked through to ATL. You need to check with the airline you are flying from Bilbao in advance. If they don't have a sharing agreement (don't know exactly what it's called), you will have to get a boarding pass for the CDG-ATL leg at CDG.

I booked my flight with Delta. The Bilbao to CDG leg is on Air France, but they are in alliance. I've never had to connect in CDG and people have told me horror stories about the immigration line and if you come in different terminals, it can be a mess.

I was just wondering because when I flew to Reykjavik, I had to pick up my bag at JFK and recheck it going through to Iceland and then had to do the same thing coming back, even though it was one ticket.

As long as you are using one ticket or one PNR, you should be able to connect smoothly. There will be special passport control facilities for those connecting which will expedite the process. If you have booked your tickets separately or you are using two separate tickets, 110 minutes is no where near sufficient time to pass through CDG.

Always check, when your bags are tagged at your point of departure, the destination airport on your tag. If your bag tags have ATL printed on them, and they should, then you will not pick them up and recheck them at CDG.

I was just wondering because when I flew to Reykjavik, I had to pick up my bag at JFK and recheck it going through to Iceland and then had to do the same thing coming back, even though it was one ticket.

If you were flying Reykjavik-JFK- ATL then yes, you would have to collect your bag at JFK because it where you entered the U.S. You always go through U.S immigration and customs at first port of entry into the country. Not sure why you had to retrieve your luggage going to Iceland if it was on the same ticket.

You should be able to check your bag through to ATL and get both boarding passes in Bilbao. If there is a long line for security or passport control at CDG, find a staff person and tell them you have a short connection. There may be a separate line or they may be able to expedite your passage through. Also, in Bilbao make sure that the luggage tag says ATL and ask the agent to add a "short connection" tag.

And just in case your bag does go astray or doesn't make the connection, take a photo of it and also make a note of the dimensions. You'll need that info for the lost baggage claim.

I think the best we have done coming through CDG is 2 hours maybe just shy of 2. Traveling on 1 ticket either entering or leaving. I like 3-4 hours to be safe. You never know when a large tour group comes through and you get stuck behind them. Or the airport staff at passport control is on break. Do you have status with Delta? Sky Priority will get you through the check in process faster but won't help much after that. Please come back and tell us how it went. Always good to here positive stories!