TNG sort of mixed up the Klingons and Romulans I think.
I think that already happened in the bridge simulator at the beginning of ST II (unless it was deliberate to remind the well-educated cadets that this was just a simulation
Borg - Americans, consuming everything through homogenization of cultures.
Ouch. A very interesting thought.
The one stereotype I'm still not entirely convinced is that the TOS Klingons presented citizens of the Soviet Union. I mean, you don't add a Russian crew member (Chekov) to appease the Soviets and then use the Klingons as carbon copies of the Red Army.
Especially with the portrayal of Kang in "Day of the Dove" and keeping the Hornblower allusions in mind, he reminded me rather of a Spanish captain (the antagonists in most of Hornblower's adventures) who tried to seize Kirk's ship (to take and claim the ship as a "prize").