I think disciplined pikemen and the arquebus put paid to knightly cavalry more than the longbow and at Agincourt the French were so ineptly handled as to perhaps make the use of the bow incidental. (and most of the French armored men at arms approached on foot and closed with the English where the battle was decided by the melee). I think the lessons of the Swiss-Burgundian War and the Spanish-French wars in early 16th Century Italy are more instructive than the 100 Years War.
Anyway, I think a division of heavy cavalry would have been right handy for Meade after the repulse of Pickett's Charge. And let's throw in some Polish lancers too.

Americans have the habit of thinking that if they don't do something, or fail to do it properly, it isn't worth doing.
Regards