In order to use proper syntax, should I use the word culture or cultures in this sentence: "Dr. Hwang contrasts American and Korean culture(s)"?
Dr. Hwang contrasts American and Korean cultures. (This seems like a passable answer but if possible, avoid this syntax altogether and consider using "compares" instead of "contrasts."
I'm having trouble finding a rule for this but I believe it's uncommon for the verb contrast to be used in this form at all.
An example from Oxford below uses, "The poem contrasts youth and age." So - it should follow that you could write "Dr. Hwang contrasts American and Korean cultures" but it is awkward stylistically.
[transitive] contrast (A and/with B) to compare two things in order to show the differences between them
It is interesting to contrast the British legal system with the American one.
The poem contrasts youth and age.
Compare and contrast the two novels.