Dude you're right. Every Tom, Dick, Harry, Susan, Jean, Bob and Charlie in N. America a Corolla. But of course in Japan it's the Civic which rules the road. Thailand has a truck load of Corollas as well. So yeah it varies from city to city, country to country.
However the world over, Corolla beats the Civic in units sold by a very very long shot. Corolla is older, let's face it. But despite their headstart I just dont like the car (although I have owned quite a few Corollas), technologically they are inferior to the Civics. Lastly, I dont like the Corolla's shape (never have, most likely never will, not a single model).
My 0.02 cents.