Can someone please tell me if I can easily visit the Normandy sites and return to Deauville on the same day. I am staying in Deauville for a few days. Thanks

Easy is always relative. If you have a car then easy will come easily.

In Bayeaux, the organized tours form up early in the morning and some form up just after lunch.

Viamichelin estimates the drive time Deuville to Bayeaux as one hour and two minutes.

Thank you. Yes, we will have a car so we will be able to visit the area.

It all depends on which sights in Normandy you want to see! Once you have that sorted out, go to mappy.com for estimates of driving time and take it from there.

Yeah, you can. We did it, stayed in Deauville and traveled to the DDay beaches one day, all the way to Mt. St. Michel one day. It was a lot of car time but it was doable.
If I did it again I would stay in Deauville to visit the DDay beaches and Honfleur, and then go to Mt. St. Michel and stay there or in the surrounding area one night.

Yes, you can!!!

While you are there, you want to walk one or more of the beaches (of course).
a maybe Pont du Hoc.

Some other things that you might want to consider:
The mueseum in Caen (Peace Museum)
The American Cemetery at Colleville
(almost 10,000 crosses)
St Mere Eglais (paratroopers freed the first village) has a small paratrooper museum.
Arromanches - one of the two artificial harbors that were built for the invasion. There is a theater with a 360 degeree movie. There is also a museum with a large model explaining the artificial harbor.
St Marie Dumont was the first village freed by land forces. It looked interesting from the bus, but I know if there is anything to see.

There was a WWII museum in Bayeaux (2002).