Vulcans = Germans when they're peaceful.
Reasoning: Look up how they behave, stereotypes of West Germany at the time were emotional robotic drones that were sort of buddies with us and shared technology.
Romulans = Germans when they're being Nazis (or potentially Austrians)
Reasoning: Extremely xenophobic, believe they're the master race. The structure of their society is almost picture perfect fascism, down to the SS/Tal Shiar.
Andorians = Scandinavians, Icelanders, and Danes
Their homeworld is icy, their folk heroes are sailors that circumnavigate things.
Klingons = Russians
Reasoning: because of when the original show was made. they even made them look like cossaks. also they became our friends when soviet union collapsed, because Gene was a hopeful commie, but all that came of it IRL was joined cooperation on the space station.
Some people think it was chinese, but at the time of TOS americans actually considered Russians to be "asiatic huns"
Rigellian = Amerindians, first nations, native american, whatever
Just look at them! Also multigender is a reference to multiple gender cultures in native americans (although natives used it as a form of punshshment, not regular gender)
Betazoids = Brits
Matriarchal society, emotion sensitive, best allies to humans.
Bolians = Canadians
Friendly, compasionate background species. Assisted suicide topic brought up when Canada was ratifying no-rescuscitation law and discussing assisted suicide.
Coridan = Spanish, including south Americans
Hello, CORIDA? Energy rich, labor force. Like fast cars. They have a conflict between Andorrans (scandies) and Vulcans (germans), which mimics early 20th century conflicts in South America. Spanish miracle of the 60s is referenced at one point I think.
Orions = Brazillians
References to Amazons and so on, neighbors to Coridans. Not really hispanic, but portuguese.
Tellarite = Italians
Warm climate, emotional, likes to argue, mostly eats veggies…
Denobulans = Indians
Population pressures, extended and weird families, breed like crazy. They're presented often as educated workers.
Bajorans = Bosnians, Albanians (and Croatians)
Hurr my religion, deep soul people, we got ethnically cleansed by the evil Cardassians/Serbs! DS9 was made during 90s, when we just got finished with Yugoslav wars.
Cardassians = Serbs
They even had a Cardassian Slobodan Milosevic substitute say the line "What will you do now, withhold my medicine?!" a reference to UN killing the real Slobodan by withholding his heart medication.
Founders = The Deep State, Globalists - the only thing that makes sense
Multiple references to them guiding the development of other species, controlling them from afar, being able to blend into and infiltrate other species, being even more ruthless than fascists, having Jem Hadar on standby as rioters-/ehem/-warriors.
Jem Hadar = American blacks, minorities, hapas
See above. Hyper aggressive from birth. Teens are essentially criminals. Controlled by Dominion via "the white" which is clearly a metaphor for crack cocaine, completely expendable. "Created" by Founders just like IRL globalists are responsible for mixed races and migrants.
Trills = Aussies
Majority of population (without symbiont) is a bunch of cucks. A small portion of the population (with symbiont) is mind-blowingly awesome hardass shitposters. One of the best friends of federation.
Vorta = SJWs and Antifa
Clones, loyal manlets.
Breen = Islamic terrorists, Taliban
Cover their faces. Historically first attacked by Klingons (Russians) in a failed invasion, huge tie to Soviet-Afghan war. Indiscriminate terrorist attacks on federation species.
Voyager species seem to be more based on whim than actual allegory, so I don't know what they mean.