Yeah, having thought about it some more, had the Luftwaffe chosen to meet the Americans above the beaches, they might have delayed the inevitable but I tend to doubt that it would have been more than a delay. Rather than proceeding on unescorted deep into Germany and risking additional Schweinfurts, the heavies might have stayed with their escort fighters and struck at lots and lots of coastal airfields until attrition took its toll on the Luftwaffe at which point deep escorted strikes could resume.
One thing I've never really understood about the Germans and perhaps someone can help me out is why they didn't try some sort of a bomblet attached to perhaps a half mile of wire and a small parachute. A plane such as an HE-111 flying just after attacking fighters (attacking fighters caused the bombers to bunch up) could approach from head on and above an unescorted formation and release hundreds of aerial mines. As these aerial mines drifted downward into the path of the bombers, when the wire struck the leading edge of a bomber's wing, the parachute above would create more drag than the bomblet below and cause the bomblet to be pulled up until it contacted the bomber's skin and detonated. The bomblet's explosive charge didn't need to be large. All it needed to do was blow a large enough hole in the bomber's skin that it would have to fall out of formation at which point German fighters could deal with it.
The brits did something similar but decided it did not work well: http://battleofbritain.devhub.com/blog/567970-world-war-ii-churchills-aerial-mines-project/