What does “communications between the tribes of the New World” refer to?
It refers to tribes talking to one another, which is a process.
What does “the Europeans’ barbarities” refer to?
It refers to what the European settlers were doing, which was taking the land, destroying tribal settlements and killing lots of people. And that’s a process.
(Okay okay… “News of the Europeans’ barbarities” does refer to a thing—the news, the information—but the embedded nominal group “the Europeans’ barbarities” still refers to a process—that’s the part we’re interested in.)
What does “the rapid spread of new conquests and settlements” refer to?
It refers to the process of rapidly conquering native tribes and establishing new settlements across the land.
Three nominal groups in one snippet that all refer to processes instead of people or things? That’s no coincidence!