Even tiny French towns have a memorial to those who died in WW I (and II and Africa, but there are fewer names). I've been in towns of 1000 people and seen the monuments with 80 names on it. The French, and British, had long memories of WW I, and did not want a repeat. This heavily influenced French strategy in WW II, they wanted to:
1. Move the war into Belgium.
2. Be on the defensive.
3. Let the Germans do mass attacks and get mowed down.
4. Hunker behind fortifications so they could hold the actual border with fewer troops (Maginot).
The French lost a generation of men in WW I, and they were suffering to have enough to fight in WW II even though they had more men, tanks, planes, etc. than the Germans. When Germany attacked Poland, the French made a desultory foray into Germany and found little resistance and retreated back into the Maginot Line. When the Germans attacked in May 1940, they rushed into Belgium to reach their defensive lines (along a river in general) and the Germans cut them off at the pivot point. The French in theory could have attacked back south and cut off the German advance, but they simply did not have an attack mentality or command structure or mobility. The British made an attack at Arras and have Rommel quite the fright, but the attack was uncoordinated and failed.
The worst outcome at D-Day I had not considered was worsening weather, as someone above noted. It was bad anyway, and later in June a terrible storm hit and really set back landing supplies (destroyed one Mulberry).
The 4th ID that landed at Utah had a fairly easy go of it though, it's hard to see how that would have failed completely unless weather was so bad they couldn't land.
But that landing zone was deep in bocage country. The Normans in that area divided their plots of land with heavy tall hedgerows.