Well, I think this may just be a case of back story that never got into the final version of the game. I can't really imagine a reason for the creators to specifically avoid the term "Cuban." Granted, Cuba and the U.S. are not on good terms (for some ridiculous reason--probably political pressure from all the powerful Cuban expatriate gangsters and casino owners currently living in the U.S. who still won't forgive Castro for exiling them). But God knows the U.S. and the Nazis didn't exactly love each other either, and Hitler's lackeys still managed to find their way into the game. :-)
I do have what I think constitutes a good reason for the Cubans investigating, however. We know the Nazis explored the mythological pyramid with a military team, presumably to try to harness whatever occult power was locked inside, to advance their imperialist agenda. It would be understandable for the Soviets, yet another expansionist superpower, to have a similar interest, especially if they were to find some documents on the matter after seizing Berlin. So, depending on when the Soviets decided upon investigating the matter, it might have been more convenient for them to carry out their military (or KGB, or whatever) investigation through the pro-Soviet Communist regime in Cuba. Perhaps this is the origin of the team of Cubans "looking for some sort of enchanted bottle."
Thus, the U.S. would be the third world superpower to try to unlock the secrets of the pyramid. Anyway, just a thought.
