The salami-like sausage the Americans call pepperoni is a distinctly Italian-American invention. It seems to have been developed around 1900, being based on the pork-only sausages of Calabria and Apulia, which often are similarly seasoned and colored, suing dried chilies.

Food historian John Mariani discusses pepperoni and other Italian-style processed meat products in his excellent book on Italian-American cookery, the misleadingly-titled How Italian Food Conquered the World.

I can't answer this but have only an additional question to ask:

In America, in addition to pepperoni we ALSO have something we call salami. Do Europeans have multiple types of salamis?

Not sure if this is appropriate here but as it's related how did Bologna become baloney?