I play quite a bit, although I'm much more casual and generally just focus on the US. I find myself identifying areas based on foliage pretty frequently. They can be super localized and after you play a few hundred or thousand maps, you just start naturally associating different areas with different plants. I'm nowhere near good enough to guess in 3 seconds based off anything, but after a few months I find I can generally spawn, not move the camera, and correctly guess I'm in 1 of like 4 states. Depending on what's visible, I can often identify the correct state immediately, although pinpointing takes a lot more time. It's just like any game: repetition and practice makes perfect.