In my mind, everything isn't exact. Some worlds are difficult for me to set a location in relation to the real world due to the blending of environments and terrain, but I basically think of them like this:
SM is like San Francisco, although I sometimes pretend it's NYC as well, the Spice District in particular. Windenburg is Western Europe to me, specifically southern Germany in the old city, or Austria along the alps in the countryside, especially where the estate is, but I sometimes imagine the countryside is England for gameplay purposes. BB is northeast USA, like coastal Maine down to The Cape and Nantucket Islands. WC is deep south US anywhere from New Orleans to Atlanta, and NC and MP are neighboring suburbs. FH is settled deep with in the Carpathian Mountains in Romania's Transylvanian region. OS is southwest US, namely Arizona. GF is in the Rocky Mountains. SD is obviously the jungles of Central and South America.
My only small annoyance about this is the immersion factor. I love being able to travel anywhere we want, but seeing the same sims in all the worlds break it a bit lol.
