If anyone is interested in some of the Omaha Beach (and general D-Day problems) the troops faced, this Master's Degree Thesis goes into detail.
http://archives.njit.edu/vol01/etd/2...td2002-069.pdf
I personally think that there were four main problems:
1. Use of heavy bombers (Flying Fortresses and Liberators) to neutralize the German beach defenses and flying these bombers at right angles to the beach, instead of using attack aircraft (such as Thunderbolts and Typhoons) and flying them along the beach defenses. The heavies were not experienced or suited to close air support and most of their bombs landed well inland, causing no trouble to the Germans but, possibly really annoying the French cows. The machine guns and cannon, as well as the bombs, from constant close air support would have least kept the German heads down...
2. The beach bombardment was too short to be effective. And the fire from the only two heavy ships assigned to Omaha Beach (a World War One battleship, USS Texas and an old British cruiser) was directed against possible heavy gun emplacements inland from the beach and not against the dug-in defenses on the bluffs overlooking the beach.
3. No use of Napalm against the bluff defenses. The Allies used napalm primarily against the Japanese. It "could" have been available for D-Day. It was used (sparingly in Europe) later in July 1944...
4. When the Allied Commander realized the decimation that the German machine gun positions on the bluffs was causing, we "should" have been ready to drop a smoke screen to protect those troops.
If D-Day had failed, the War would have been extended by a year or two and who knows what the war weary allies might have settled for. The success of the landings was due more to the bulldog courage of American, British and Canadian troops than to the ability of their generals...