For instance, when Europeans first traveled to the Americas and began interacting with native populations, how did either population begin the process of building mutual understanding and learning the other’s language? I’ve never come across a history book that discusses these linguistic processes in any way.
I answered this very question three months ago. I hope it helps:
https://www.reddit.com/r/AskHistorians/comments/erm9fy/how_did_the_spanish_conquistadors_and_early/
In addition to /u/TywinDeVillena 's answer you may also be interested in my answer on Mexico, especially on the important role of the native translator Malintzin/Malinche during the Spanish-Aztec war: https://www.reddit.com/r/AskHistorians/comments/b9pqhk/when_hernan_cortez_and_the_spaniards_arrivedin/ek6ckii/
We also have a Faq section on this with threads on other regions: https://www.reddit.com/r/AskHistorians/wiki/language#wiki_cross-cultural_communication_and_lingua_francas
To add a caveat for your question: translation was not merely a neutral exchange in early Spanish America. In Mexico for example, Cortés used native translators to form important alliances with Nahua states; and in some cases for preparing massacres. This would heavily influence the fall of the Mexica and in the longer run lead to enslavement, forced labor and resettlements of native populations among many other developments. So just a reminder to say that translation was (and is) inherently political.
Hope this helps!