For me, Willow Creek and Magnolia prominade are in the same place. Newcrest sometimes is as well, but I'm so desperate for an England world that I often use it to build houses I'd see here at home. Then Windenburg is in another country, since it is Europe. Oasis Springs I imagine to be a hotter climate in the same country as Willow Creek (I think of it as California) OR somewhere like Spain, Portugal. Depends on the save.
I do wish sims from other towns wouldn't randomly walk through other worlds because it breaks this immersion for me. It's hard to make myself believe Windenburg is not just another part of America when Bella Goth and Eliza Pancake walk down the street.
