Ancient Longball
There was a rich tradition of bat-and-ball games outside of England in other parts of Europe, and many of them have striking (pun intended) similarities with each other. What contributions could these other European bat and ball sports have brought to baseball, especially as distinct waves of immigration came from Europe? This question has not been investigated enough, but I think a big reason for the success of “American Baseball” was that Europeans from all sorts of backgrounds embraced the game because it was similar to a bat and ball game of their youth in Europe.