I certainly don't have the info/sources on this one that Mahross does, but...

Wilconqr, some info from a video set I have- "Tanks", British production videos, not sure offhand who did them...
This video sets sets out the idea that as far as the "funnies" were concerned (the specialized sherman tanks), there simply were not enough of them to supply the American landing beaches in addition to the British and Canadian beaches.
As far as the Sherman DD tanks deploying for the American sector- from what the video, and a couple other sources asy, I've always gotten the idea that the Sherman DDs were deployed in too deep water too far from the beach. In addition, apparently there was a cross-wind for the American tanks, which further caused them to lean towards the side and flounder.

Erich- that IS a good question, isn't it! From the same video referenced above, I do get the idea that by the time Goodwood came around, the Germans (1st SS) were down to about 100 operational AFVs. I guess the allied A/C did catch quite a few german tanks... but I also guess that some were just SO camoflaged and dug in and whatnot- probably not visible unless they were to move.

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Seriously, all today is missing is free cotton candy and the annual Bay State Hooker Parade to make it any better.