Never assume that Los Angles is the /real/ Los Angles, etc. I do not know much about all the cities in the world. I've lived in two big cities, and that's it. If you want a game set in Cincinnati, Colorado Springs, Lebanon, OH or Athens, OH, I can be very specific. Otherwise assume stuff to be made up.
Also, historical events might not have happened, etc. Though unless I say so, assume everything you know at the beginning of the game is what has happened up to that date in the world as we know it.
Thanks,
Tet