Knight Templar
Commodore
One former enemy, one current enemy, one black woman, a Scotsman, a devilish looking alien and two Americans. .
"former enemy" I assume you mean Chekov who was Russian of course. But he could hardly be considered a major character in the OS as he was not even introduced until the second season.
And even then, Russians had been allies of the U.S. in the past notably in World War Two.
"current enemy" ??? Not sure who you are referring to unless it is possibly Sulu. Of course during the original series we never even came close to find out where Sulu was from.
Until The Voyage Home when we find out he was from....San Francisco.
America has a very long and well established connection to Scotland.
And even in the late 1960s there were black women serving in the military.
Finally, I never found Spock particularly "demonic looking".