It's not precisely what you're looking for, but given that European images of Native American cultures played major roles in such key European cultural movements as Romanticism (via Rousseau), Communism (via Marx and perrticularly Engels), and 20th century primitivism and the counter-culture (From Gaugin to Mgt. Mead), maybe it would be interesting to trace the genealogies of these images of what became the "noble savage" to ask whether anything of substance was imported from actual American cultures, or whether the whole thing was essentially a projection. You could start by contrasting Montaigne with Bartolomé de las Casas, for instance.

I also think it's quite likely that there is a body of literature (including texts by people of Native American descent) discussing the gaps between European representations of American cultures, and the realities.

Finally, the work of Michael Taussig might be interesting. Particularly his book Mimesis and Alterity.

it was mostly crops and food that made it back

This is not correct at all. For one thing, significant energy that eventually led to the identity of "Spain" itself was forged abroad, among the conquistadors and settlers in the Americas.

• M. J. Rodriguez-Salgado, "Christians, Civilised and Spanish: Multiple Identities in Sixteenth-Century Spain," Trans. Royal Historical Soc., Vol. 8 (1998), pp. 233-251.

• H. Kamen, "Spain's Road to Empire," ISBN-13: 9780141927329 0141927321, 2003.

As mentioned, Spanish view of the "others" evolved significantly, and is very informative in lieu of the Valladolid debate between Las Cases and Sépulveda. It greatly influenced the humanist movement in Early Modern and Renaissance era.

I'm sorry your professor is hugely under-informed.

Questions of cultural back-flows from Empire are hard, hard enough that I'm doing a DPhil on an element of this issue, and having a trouble both with sources and most often with the credulity of my peers (as you with your professor).

First, the canonical texts about this are almost all concerned with the Eastern, South Asian and African Empires; there is very little on South American Empire. For example, Hobson - (2004) The Eastern Origins of Western Civilization - argues that most turning points in modern Western technology, politics, law, and culture were only accomplished via the assimilation of ideas from the East. Most of Bernard Cohn's work has it written throughout that the process of reshaping Indian society into intelligible (and governable) chunks had a profound impact on the modern British governmental mind (see for example Colonialism and its Forms of Knowledge). Others have shown the ways in which British activists learned from colonized peoples, and brought home the experience of empire, in ways that changed their oppositional politics, see for instance Hall (2002) Civilising Subjects. Again, though, this work is largely about India.

There are a litany of reasons for the "Eastern" bias. Perhaps chief among them is the fact that interaction with the Middle East and East Asia had been an established fact of European life for a good long while. Trade routes with Asia were long established and crucial to European wealth; Venice's prominence was mostly due to its position as key link to Eastern trade, and discourse at the time very clearly considered the city to be a quasi-Eastern culture. Crusading symbols 'bringing the East home' (Lion, etc) abound in European Heraldry. Borges even argues that Europe's episodic literary tradition only came about as a response to translation of the Thousand and One Nights (in Seven Nights 1984). The thought of the Ottoman, and "the Turk" as the canonical other of Europe is almost a cliché of International Relations at this point (see Neumann 1999 Uses of the other:" the East" in European identity formation). Montesquieu chose a made-up 'Persian' as the outsider poised to ridicule European society. Voltaire does pretty succinct justice to the attitude here:

If as a philosopher one wishes to instruct oneself about what has taken place on the globe, one must first of all turn one’s eyes towards the East, the cradle of all arts, to which the West owes everything.

This bias also has a lot to do with who colonized whom: the British style of Empire after 1857 was more penetratingly "cultural" than the Spanish or French modes (see Pagden 1995 Lords of All the World for a comparison of early modern empires, and Mamdani 1996 Citizen and Subject for the "indirect" cultural way of governing, specifically focused on British Africa). If you ever get a chance to browse Oxford's Ashmolean, which claims to be the first purpose-built public museum in the world, its guiding organizing principle is pretty openly "cultural artifacts we appropriated from elsewhere and made our own." But again, 'elsewhere' was largely Asia. Obviously you are asking about Spanish colonization, but I mention all of this because the historiography of cultural flows in empire is pretty heavily dominated by the history of Britain.

Finally, at least one scholar argues a bit paradoxically that Latin America's exclusion from these conversations has to do with its perception as being 'sort of western'.

This [lack of attention] is true of developing countries in general, but Latin America in particular because of its early emergence and the widespread perception that independence merely saw the continuing dominance of ‘Western’ settler elites. This perception has supported the argument that Latin America was essentially part of the West and therefore not worthy of separate consideration. Recent work on ‘non-Western IR theory’ corroborates this view by mostly excluding mention of Latin America, at least until the mid-twentieth century. (Fawcett 2012 Between West and non-West: Latin American Contributions to International Thought)

Latin America, she suggests, wasn't quite "other" enough.

I'm sorry for a whole lot of "it's hard" instead of a real solution, but this is the lay of the land from what I've seen. I may be suffering from a language barrier; if someone on here works in Spanish they could have a better answer. Finally, you might find a spark of inspiration somewhere in Borges' nonfiction. He's a great scholar of the Western tradition, writing very much from a South American vantage point. And he's a damn fun read. If you can find answers to this question, you can at least rest assured that you'll be contributing something seriously worthwhile to our understanding of the world.

Edit: Fixed quotation formatting.

Thank you so much! Very helpful insight! Much appreciated!

I don't know about Spain, but Native North Americas introduced the front crawl swimming technique to Britain.

http://www.fina.org/H2O/index.php?option=com_content&view=article&id=901&Itemid=565

Not exactly a societal change, but still a technology transfer.

I see most refer to native Americans while I do not see you have to limit yourself to those. Spanish settlers did mix significantly and like in North America generations would start to be born in the American continent. This led to what we call the criollos or "creole" society, it may be worth exploring how if any this class pushed cultural inspirations back into the Old Continent.