I begin every seminar with a quiz. This week, I had a six or seven texts and had them see if you could tell whether the author was peninsular or Spanish American. The result was that nobody could tell the difference between the lyrical language of Spain and that of Latin America. Sure, people guessed right once in a while, but with no confidence in their judgment and not at a rate larger than chance. In cases where virtually the whole class agreed, they were just as likely to be wrong as right, as in the case of a Cintio Vintier sonnet that everyone thought had to have been written in Spain.
This depended on not choosing any poem that was well known, or any that had regional variants in an explicit way that would give it away. But on the other hand it wasn't hard to find language that was more neutral (geographically speaking). I found my examples in about 15 minutes, or less than 2 minutes per example. I even stuck one of my own poems in the mix (they thought it was either from Spain or Spanish America, in equal numbers).
The students in this graduate course are from Spanish speaking countries (Spain and Colombia, Argentina, Mexico) and from the US. Students from any particular place did not do any better. Once in a while someone had plausible sounding reason for their guess, and it turned out to be correct. These are future Spanish professors so you can't argue that they simply are smart enough yet to know the difference. I doubt I could pass my own test unless I happened to recognize a particular poet.
This leads me to reflect on that idiot in CHE a while back who wrote that the teaching of peninsular Spanish in US universities was so colonialist, that having a lot of people with peninsular Spanish on the faculty was such a bad thing.